Spin-valve magnetoresistive thin film element

ABSTRACT

An antiferromagnetic layer is formed of a PtMn alloy which has high blocking temperature and further generates a great exchange coupling magnetic field with a first pinned magnetic layer. Further, by appropriately adjusting the film thickness ratio of the first pinned magnetic layer and a second pinned magnetic layer, the film thickness of a nonmagnetic electrically conductive layer and the antiferromagnetic layer, and so forth, an exchange coupling magnetic field of at least 500 (Oe) or greater, preferably 1,000 (Oe) or greater, can be obtained.

RELATED SUBJECT MATTER

Related subject matter is disclosed in commonly-assigned, patentapplications having Ser. No. 09/357,915 filed Jul. 20, 1999 and Ser. No.09/861,413 filed May 18, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spin-valve magnetoresistive thin filmelement which changes in electric resistance according to therelationship between the pinned magnetization direction of a pinnedmagnetic layer and the magnetization direction of a free magnetic layerwhich is affected by external magnetic fields. More particularly, thepresent invention relates to a spin-valve magnetoresistive thin filmelement wherein the pinned magnetic layer is divided into two layers,such that the magnetization (Ferri-state) between the two pinnedmagnetic layers can be maintained in a thermally stabilized state. Thepresent invention also relates to a thin film magnetic head using thisspin-valve magnetoresistive thin film.

The present invention also relates to a spin-valve magnetoresistive thinfilm element which changes in electric resistance according to therelationship between the pinned magnetization direction of a pinnedmagnetic layer and the magnetization direction of a free magnetic layerwhich is affected by external magnetic fields, and particularly relatesto a spin-valve magnetoresistive thin film element wherein themagnetization of the pinned magnetic layer can be maintained in a morestabilized state by causing a sensing current to flow in an appropriatedirection, and also relates to a thin film magnetic head using thisspin-valve magnetoresistive thin film element.

The present invention also relates to a spin-valve magnetoresistive thinfilm element which changes in electric resistance according to therelationship between the pinned magnetization direction of a pinnedmagnetic layer and the magnetization direction of a free magnetic layerwhich is affected by external magnetic fields, and particularly relatesto a method for manufacturing a spin-valve magnetoresistive thin filmelement wherein magnetization control of the pinned magnetic layer canbe performed in an appropriate manner of appropriately adjusting themagnetic moment of the pinned magnetic layer, and the direction and sizeof the magnetic field to be applied during thermal treatment, and alsorelates to a method for manufacturing a thin film magnetic head usingthis spin-valve magnetoresistive thin film element.

2. Description of the Related Art

A spin-valve magnetoresistive thin film element is a type of GMR (giantmagnetoresistive) element which makes use of the giant magnetoresistance effect, and is used for detecting recorded magnetic fieldsfrom recording mediums such as hard disks and the like.

The spin-valve magnetoresistive thin film element has severaladvantages, such as having a relatively simple structure for a GMRelement. Further, the spin-valve magnetoresistive thin film element canchange resistance under weak magnetic fields.

In its simplest form, the spin-valve magnetoresistive thin film elementis comprised of an antiferromagnetic layer, a pinned magnetic layer, anonmagnetic electrically conductive layer, and a free magnetic layer.FIG. 28 is a cross-sectional view of a known spin-valve magnetoresistivethin film element, viewed from the side opposing a recording medium.

Also, FIG. 29 is a sideways cross-sectional diagram schematicallyillustrating the spin-valve magnetoresistive thin film element shown inFIG. 28.

Reference numeral 1 denotes a base layer formed of Ta (tantalum) forexample, and formed on this base layer 1 is formed an antiferromagneticlayer 2, and further a pinned magnetic layer 3 is formed on theantiferromagnetic layer 2.

The pinned magnetic layer 3 is formed in contact with theantiferromagnetic layer 2, thereby generating an exchange couplingmagnetic field (exchange anisotropic magnetic field) at the interfacebetween the pinned magnetic layer 3 and the antiferromagnetic layer 2,and the magnetization of the pinned magnetic layer is pinned in the Ydirection in the Figure, for example.

Formed upon the pinned magnetic layer 3 is a nonmagnetic electricallyconductive layer 4 formed of Cu or the like, and further formed upon thenonmagnetic electrically conductive layer 4 is a free magnetic layer 5.Formed on either side of the free magnetic layer 5 are hard magneticbias layers 6 formed of a Co—Pt (cobalt-platinum) alloy for example, andthe hard magnetic bias layers 6 are magnetized in the direction X in theFigure, so the magnetization of the free magnetic layer 5 is aligned inthe direction X in the Figure. Accordingly, the fluctuationmagnetization of the free magnetic layer 5 and the pinned magnetizationof the pinned magnetic layer 3 are in an intersecting relationship.Incidentally, reference numeral 7 denotes a protective layer formed ofTa or the like, and reference numeral 8 denotes a lead layer formed ofCu or the like.

With this spin-valve magnetoresistive thin film element, a sensingcurrent flows from the lead layer 8 either in the direction of X shownin the Figure or in the direction opposite to X shown in the Figure,with mainly the nonmagnetic electrically conductive layer 4 as thecenter. Then, when the magnetization of the free magnetic layer 5aligned in the direction X in the Figure fluctuates due to magneticfield leaking from the recording medium (such as a hard disk), electricresistance changes according to the relationship between themagnetization of the free magnetic layer 5 and the magnetization of thepinned magnetic layer 3 pinned in the direction Y in the Figure, and amagnetic field leaking from the recording medium is detected by voltagechange based on the change in the electric resistance values.

Also, with known arrangements, FeMn alloys, NiO, NiMn alloys, etc., areused for the antiferromagnetic layer 2. Of these examples, using FeMnalloys or NiO as the antiferromagnetic material does not necessitatethermal treatment in order to generate an exchange coupling magneticfield at the interface between the antiferromagnetic layer 2 and thepinned magnetic layer 3, but using NiMn as the antiferromagneticmaterial does necessitate thermal treatment.

Now, with known arrangements, NiMn alloys, FeMn alloys, NiO, etc., areused as antiferromagnetic materials for the antiferromagnetic layer 2.

However, of these, the blocking temperature of FeMn alloys and NiOalloys in particular is 200° C. or lower, meaning that these materialsare lacking in stability.

Particularly, in recent years, the number of revolutions of therecording medium and the amount of sensing current flowing from the leadlayer 8 have been increasing, and the environmental temperature withinthe device reaches high temperatures of 200° C. for example, or higher.Accordingly, using an antiferromagnetic material with low blockingtemperature as the antiferromagnetic layer 2 of the spin-valvemagnetoresistive thin film element reduces the exchange couplingmagnetic field (exchange anisotropic magnetic field) generated at theinterface between the antiferromagnetic layer 2 and the pinned magneticlayer 3. The result is that the magnetization of the pinned magneticlayer 3 cannot be appropriately pinned in the direction Y in the Figure,consequently allowing ΔMR (rate of change of resistance) to drop.

The blocking temperature is determined solely by the antiferromagneticmaterial comprising the antiferromagnetic layer 2. Thus, even if thestructure of the spin-valve magnetoresistive thin film element isimproved, the blocking temperature itself cannot be raised.

For example, U.S. Pat. No. 5,701,223 discloses an invention wherein thestructure of the pinned magnetic layer is improved and the exchangecoupling magnetic field can be improved. However, this invention usesNiO as the antiferromagnetic layer, so the blocking temperature isaround 200° C. Thus, even though the exchange coupling magnetic fieldmay be increased at room temperature, the exchange coupling magneticfield of the spin-valve magnetoresistive thin film element becomessmaller while the recording medium is running as the environmentaltemperature within the device reaches the vicinity of 200° C. or higher.The exchange coupling magnetic field may becomes 0, so no ΔMR can beobtained at all.

On the other hand, NiMn alloys have higher blocking temperatures thanNiO or FeMn alloys, but the properties of these alloys such ascorrosion-resistance and the like are poor, so an antiferromagneticmaterial with even higher blocking temperatures and excellent propertiesthereof such as corrosion-resistance is being demanded.

Also, as described above, the sensing current flows from the lead layer8 with mainly the nonmagnetic electrically conductive layer 4 having lowratio resistance as the center, so a sensing current magnetic field isformed by the corkscrew rule because of the sensing current that iscaused to flow. This sensing current magnetic field affecting the pinnedmagnetization of the pinned magnetic layer 3.

For example, as shown in FIG. 29, the magnetization of the pinnedmagnetic layer 3 is directed in the direction of Y in the Figure. But,if the sensing current magnetic field generated by causing sensingcurrent to flow is directed in the direction opposite to Y in the Figureat the portion of the pinned magnetic layer 3, the direction of thepinned magnetization of the pinned magnetic layer 3 and the direction ofthe sensing current magnetic field do not match, so the pinnedmagnetization is affected by the sensing current magnetic field andwavers. This is a problem in that the state of magnetization becomesunstable.

Particularly, if an antiferromagnetic material such as an NiO or FeMnalloy which produces only a small exchange coupling magnetic field(exchange anisotropic magnetic field) generated at the interface betweenthe pinned magnetic layer 3 and the antiferromagnetic layer 2, and whichhas low blocking temperature, is used for the antiferromagnetic layer 2,the deterioration of the pinned magnetism at the pinned magnetic layer 3is marked if the pinned magnetization direction of the pinned magneticlayer 3 and sensing current magnetic field direction are facing oppositedirections, and destruction may occur such as the inversion of pinnedmagnetism.

In recent years, there is a trend to use a large sensing current inorder to deal with higher densities. However, it is known that causing asensing current of 1 mA to flow generates a sensing current magneticfield of approximately 30 (Oe), and further that the element temperaturerises by about 150° C. Thus, if several tens of mA of the sensingcurrent is caused to flow, this will result in a sudden rise in thetemperature of the element, and generate a massive sensing currentmagnetic field. Accordingly, in order to improve the thermal stabilityof the pinned magnetization of the pinned magnetic layer 3, anantiferromagnetic material with a high blocking temperature and whichproduces a large exchange coupling magnetic field (exchange anisotropicmagnetic field) at the interface between the pinned magnetic layer 3 andthe antiferromagnetic layer 2 needs to be selected, and the sensingcurrent needs to be directed in an appropriate direction so themagnetization of the pinned magnetic layer 3 is not destroyed by thesensing current magnetic field.

U.S. Pat. No. 5,701,223 discloses an invention wherein the pinnedmagnetic layer is divided into two layers and the magnetization of thetwo pinned magnetic layers is in an antiparallel state, whereby a largeexchange coupling magnetic field can be obtained.

However, the antiferromagnetic layer disclosed here is NiO, and NiO hasa low blocking temperature of around 200° C., and only a small exchangecoupling magnetic field (exchange anisotropic magnetic field) isgenerated at the interface between the pinned magnetic layer and theantiferromagnetic layer.

Particularly, in recent years, there is a trend to increase the rotatingspeed of the recording medium and increase the sensing current in orderto deal with higher densities, which causes the environmentaltemperature within the device to rise. Thus, if NiO is used for theantiferromagnetic layer, the exchange coupling magnetic field issmaller, meaning that it is difficult to appropriately carry outmagnetization control of the pinned magnetic layer.

On the other hand, NiMn alloys have a higher blocking temperature thanthe NiO, and the exchange coupling magnetic field (exchange anisotropicmagnetic field) is also greater. Also, X—Mn alloys (wherein X is Pt, Pd,Ir, Rh, Ru) using elements of the platinum group have come into focus asan antiferromagnetic material which has blocking temperature around thatof NiMn alloys, a large exchange coupling magnetic field, andcorrosion-resistance far better than NiMn alloys.

Employing such X—Mn alloys using elements of the platinum group as theantiferromagnetic layer, and further dividing the pinned magnetic layerinto two layers should facilitate the obtaining a greater exchangecoupling magnetic field as compared to using NiO for theantiferromagnetic layer.

Presently, such X—Mn alloys using elements of the platinum group need tobe annealed in a magnetic field (thermal treatment) following formationof the film, in order to generate an exchange coupling magnetic field atthe interface between the pinned magnetic layer and theantiferromagnetic layer, as is true with the case of NiMn alloys, aswell.

However, unless the size and direction of the magnetic field appliedduring the thermal treatment, and the magnetic moment (saturationmagnetization Ms•film thickness t) of the two divided pinned magneticlayers are appropriately adjusted, the magnetization of the two dividedpinned magnetic layers cannot be pinned in a stable antiparallel state.Also, particularly, with so-called dual spin-valve magnetoresistive thinfilm elements (wherein the pinned magnetic layers are formed above andbelow the free magnetic layer with the free magnetic layer as the centerthereof), the magnetization direction of the two pinned magnetic layersformed above and below the free magnetic layer must be appropriatelycontrolled, or ΔMR (the rate of resistance change) drops, causingproblems such that only a small reproduction output can be obtained.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve theabove-described problems with the known art, and accordingly, it is anobject of a first aspect of the present invention to provide aspin-valve magnetoresistive thin film element and a thin film magnetichead using this spin-valve magnetoresistive thin film element that isthermally stable and capable of increasing the exchange couplingmagnetic field, by improving the structure of the pinned magnetic layerand the material comprising the antiferromagnetic layer in particular,and further appropriately adjusting the film thickness of the pinnedmagnetic layer.

Similarly, it is an object of a second aspect of the present inventionto provide a spin-valve magnetoresistive thin film element and a thinfilm magnetic head using this spin-valve magnetoresistive thin filmelement that is capable of maintaining the magnetization state of thepinned magnetic layer in a thermally stable manner, by improving thestructure of the pinned magnetic layer and the material comprising theantiferromagnetic layer in particular, and further controlling thedirection in which the sensing current is caused to flow in anappropriate direction.

Also, it is an object of a third aspect of the present invention toprovide a method for manufacturing a spin-valve magnetoresistive thinfilm element and a thin film magnetic head using this spin-valvemagnetoresistive thin film element that is capable of maintaining themagnetization of two pinned magnetic layers in a stable antiparallelstate, by appropriately controlling the magnetism moment of a pinnedmagnetic layer which has been divided into two layers, and the directionand size of a magnetic field applied during thermal treatment, andfurther capable of obtaining high ΔMR around that of known arrangements.

To this end, a first aspect of the present invention provides aspin-valve magnetoresistive thin film element, comprising: anantiferromagnetic layer; a pinned magnetic layer formed in a mannercontacting the antiferromagnetic layer, wherein the magnetizingdirection is pinned by the exchange coupling magnetic field between thepinned magnetic layer and the antiferromagnetic layer; and a nonmagneticelectrically conductive layer formed between a free magnetic layer andthe pinned magnetic layer. The magnetizing direction of the freemagnetic layer is aligned so as to intersect with the magnetizingdirection of the pinned magnetic layer. The pinned magnetic layer isdivided into two layers with a nonmagnetic intermediate layer introducedtherebetween. Here, with the pinned magnetic layer which comes incontact with the antiferromagnetic layer as a first pinned magneticlayer and with the pinned magnetic layer which comes in contact with thenonmagnetic electrically conductive layer as a second pinned magneticlayer, (the film thickness of the first pinned magnetic layer)/(the filmthickness of the second pinned magnetic layer) is in a range of 0.33 to0.95 or 1.05 to 4.

According to the present invention, (the film thickness of the firstpinned magnetic layer)/(the film thickness of the second pinned magneticlayer) is preferably in a range of 0.53 to 0.95 or 1.05 to 1.8.

Also, according to the present invention, it is preferable that the filmthickness of the first pinned magnetic layer and the film thickness ofthe second pinned magnetic layer are both in a range of 10 to 70ängström, and that |the film thickness of the first pinned magneticlayer minus the film thickness of the second pinned magnetic layer|≧2ängström.

Further, with the present invention, it is even more preferable that thefilm thickness of the first pinned magnetic layer and the film thicknessof the second pinned magnetic layer are both in a range of 10 to 50ängström, and that |the film thickness of the first pinned magneticlayer minus the film thickness of the second pinned magnetic layer|≧2ängström.

Also, with the present invention, the free magnetic layer may be dividedinto two layers with a nonmagnetic intermediate layer introducedtherebetween.

According to the present invention, the spin-valve magnetoresistive thinfilm element may comprise a single spin-valve magnetoresistive thin filmelement consisting of one layer each of the antiferromagnetic layer,first pinned magnetic layer, nonmagnetic intermediate layer, secondpinned magnetic layer, nonmagnetic electrically conductive layer, andfree magnetic layer.

If the free magnetic layer divided into two layers, the free magneticlayer is formed to the side coming into contact with the nonmagneticelectrically conductive layer serves as a first free magnetic layer andthe other free magnetic layer as a second free magnetic layer.

If the spin-valve magnetoresistive thin film element is a dualspin-valve magnetoresistive thin film element comprising: nonmagneticelectrically conductive layers formed above and below with the freemagnetic layer as the center; the three layers of the second pinnedmagnetic layer/nonmagnetic intermediate layer/first pinned magneticlayer formed above one of the nonmagnetic electrically conductive layerand below the other nonmagnetic electrically conductive layer; andantiferromagnetic layers formed above one of the first pinned magneticlayers and below the other first pinned magnetic layer; wherein, of thefree magnetic layer divided into two layers, one free magnetic layerserves as a first free magnetic layer and the other free magnetic layeras a second free magnetic layer.

In this aspect of the invention, the value of (the film thickness of thefirst free magnetic layer/the film thickness of the second free magneticlayer) is preferably in a range of 0.56 to 0.83 or 1.25 to 5, and morepreferably in a range of 0.61 to 0.83 or 1.25 to 2.1.

Also, the present invention provides a spin-valve magnetoresistive thinfilm element, comprising: an antiferromagnetic layer; a pinned magneticlayer formed in a manner contacting the antiferromagnetic layer. Themagnetizing direction is pinned by the exchange coupling magnetic fieldbetween the pinned magnetic layer and the antiferromagnetic layer bymeans of thermal treatment in a magnetic field. A nonmagneticelectrically conductive layer is formed between a free magnetic layerand the pinned magnetic layer. The magnetizing direction of the freemagnetic layer is aligned so as to intersect with the magnetizingdirection of the pinned magnetic layer. The pinned magnetic layer isdivided into two layers with a nonmagnetic intermediate layer introducedtherebetween. Here, with the pinned magnetic layer which comes incontact with the antiferromagnetic layer as a first pinned magneticlayer and with the pinned magnetic layer which comes in contact with thenonmagnetic electrically conductive layer as a second pinned magneticlayer, and with the product of saturation magnetization Ms and filmthickness t as the magnetic film thickness (magnetic moment), (themagnetic film thickness of the first pinned magnetic layer)/(themagnetic film thickness of the second pinned magnetic layer) is in arange of 0.33 to 0.95 or 1.05 to 4.

With the present invention, it is preferable that (the magnetic filmthickness of the first pinned magnetic layer)/(the magnetic filmthickness of the second pinned magnetic layer) be in a range of 0.53 to0.95 or 1.05 to 1.8.

Also, with the present invention, it is preferable that the magneticfilm thickness of the first pinned magnetic layer and the magnetic filmthickness of the second pinned magnetic layer are both in a range of 10to 70 (ängström tesla), and that |the magnetic film thickness of thefirst pinned magnetic layer minus the magnetic film thickness of thesecond pinned magnetic layer|≧2 (ängström tesla).

Further, with the present invention, it is even more preferable that thefilm thickness of the first pinned magnetic layer and the film thicknessof the second pinned magnetic layer are both in a range of 10 to 50(ängström tesla), and that |the magnetic film thickness of the firstpinned magnetic layer minus the magnetic film thickness of the secondpinned magnetic layer|≧2 (ängström tesla).

Also, with the present invention, the free magnetic layer may be dividedinto two layers with a nonmagnetic intermediate layer introducedtherebetween.

According to the present invention, the spin-valve magnetoresistive thinfilm element may comprise a single spin-valve magnetoresistive thin filmelement consisting of one layer each of the antiferromagnetic layer,first pinned magnetic layer, nonmagnetic intermediate layer, secondpinned magnetic layer, nonmagnetic electrically conductive layer, andfree magnetic layer.

If the free magnetic layer divided into two layers, the free magneticlayer formed to the side coming into contact with the nonmagneticelectrically conductive layer serves as a first free magnetic layer andthe other free magnetic layer as a second free magnetic layer.

If the spin-valve magnetoresistive thin film element is a dualspin-valve magnetoresistive thin film element comprising: nonmagneticelectrically conductive layers formed above and below with the freemagnetic layer as the center; the three layers of the second pinnedmagnetic layer/nonmagnetic intermediate layer/first pinned magneticlayer formed above one of the nonmagnetic electrically conductive layerand below the other nonmagnetic electrically conductive layer; andantiferromagnetic layers formed above one of the first pinned magneticlayers and below the other first pinned magnetic layer; wherein, of thefree magnetic layer divided into two layers, one free magnetic layerserves as a first free magnetic layer and the other free magnetic layeras a second free magnetic layer.

In this aspect of the invention, the value of (the magnetic filmthickness of the first free magnetic layer/the magnetic film thicknessof the second free magnetic layer) is preferably in a range of 0.56 to0.83 or 1.25 to 5, and more preferably in a range of 0.61 to 0.83 or1.25 to 2.1.

Also, with the present invention, it is preferable that the nonmagneticintermediate layer introduced between the first pinned magnetic layerand second pinned magnetic layer be formed of one of the following, orof an alloy of two or more thereof: Ru, Rh, Ir, Cr, Re, and Cu.

Further, with the present invention, the spin-valve magnetoresistivethin film element may comprise an antiferromagnetic layer below the freemagnetic layer, and in this arrangement, it is preferable that thethickness of the nonmagnetic intermediate layer introduced between thefirst pinned magnetic layer formed so as to come in contact with theantiferromagnetic layer and the second pinned magnetic layer formed soas to come in contact with the nonmagnetic electrically conductive layerbe in a range of 3.6 to 9.6 ängström, or more preferably, in a range of4.0 to 9.4 ängström.

Or, the spin-valve magnetoresistive thin film element may comprise anantiferromagnetic layer above the free magnetic layer, and in thisarrangement, it is preferable that the thickness of the nonmagneticintermediate layer introduced between the first pinned magnetic layerformed so as to come in contact with the antiferromagnetic layer and thesecond pinned magnetic layer formed so as to come in contact with thenonmagnetic electrically conductive layer be in a range of 2.5 to 6.4ängström or 6.6 to 10.7 ängström, or more preferably, in a range of 2.8to 6.2 ängström or 6.8 to 10.3 ängström.

Also, with the present invention, it is preferable that theantiferromagnetic layer be formed of a PtMn alloy.

Also, with the present invention, the antiferromagnetic layer may beformed of an X—Mn alloy (wherein X is one or a plurality of thefollowing elements: Pd, Ir, Rh, Ru, and Os), or formed of a PtMn—X′alloy (wherein X′ is one or a plurality of the following elements: Pd,Ir, Rh, Ru, Os, Au, and Ag).

According to the present invention, the spin-valve magnetoresistive thinfilm element may comprise a single spin-valve magnetoresistive thin filmelement consisting of one layer each of the antiferromagnetic layer,first pinned magnetic layer, nonmagnetic intermediate layer, secondpinned magnetic layer, nonmagnetic electrically conductive layer, andfree magnetic layer. With this arrangement, it is preferable that thethickness of the antiferromagnetic layer be in a range of 90 to 200ängström, and even more preferably in a range of 100 to 200 ängström.

Or, the spin-valve magnetoresistive thin film element may be a dualspin-valve magnetoresistive thin film element comprising: nonmagneticelectrically conductive layers formed above and below with the freemagnetic layer as the center; the three layers of the second pinnedmagnetic layer/nonmagnetic intermediate layer/first pinned magneticlayer formed above one of the nonmagnetic electrically conductive layerand below the other nonmagnetic electrically conductive layer; andantiferromagnetic layers formed above one of the first pinned magneticlayers and below the other first pinned magnetic layer; and with thisarrangement, it is preferable that the thickness of theantiferromagnetic layer be in a range of 100 to 200 ängström, and evenmore preferably in a range of 110 to 200 ängström.

Also, it is preferable that the nonmagnetic intermediate layerintroduced between the first free magnetic layer and second freemagnetic layer be formed of one of the following, or of an alloy of twoor more thereof: Ru, Rh, Ir, Cr, Re, and Cu.

It is preferable that the thickness of the nonmagnetic intermediatelayer be 5.5 to 10.0 ängström, and more preferably, 5.9 to 9.4 ängström.

Further, a thin film magnetic head according to the present inventioncomprises shield layers formed above and below the spin-valvemagnetoresistive thin film element, with gap layers introducedtherebetween.

With the present invention, the pinned magnetic layer making up thespin-valve magnetoresistive thin film element is divided into twolayers, with a nonmagnetic intermediate layer introduced between thepinned magnetic layers divided into two layers.

The magnetization of the divided two pinned magnetic layers aremagnetized so as to be in an antiparallel state, and also are in aso-called Ferri-state wherein the magnitude of the magnetic moment(magnetic film thickness) of one pinned magnetic layer differs from thatof the magnetic moment of the other pinned magnetic layer. The exchangecoupling magnetic field (RKKY interaction) generated between the twopinned magnetic layers is very large, around 1,000 (Oe) to 5,000 (Oe),so the two pinned magnetic layers are in a very stable state ofantiparallel magnetization.

Now, one of the pinned magnetic layers magnetized in the antiparallelstate (Ferri-state) is formed so as to be in contact with theantiferromagnetic layer, and the magnetization of the pinned magneticlayer which is in contact with the antiferromagnetic layer (hereafterreferred to as the “first pinned magnetic layer”) is fixed in thedirection away from a plane facing a recording medium for example (i.e.,the height direction), by the exchange coupling magnetic field (exchangeanisotropic magnetic field) generated at the interface between thepinned magnetic layer and the antiferromagnetic layer. Accordingly, themagnetization of the pinned magnetic layer facing the first pinnedmagnetic layer with a nonmagnetic intermediate layer introducedtherebetween (hereafter referred to as the “second pinned magneticlayer”) is pinned in a state antiparallel with the magnetization of thefirst pinned magnetic layer.

With the present invention, the portion that has been conventionallycomprised of the two layers of the antiferromagnetic layer and pinnedmagnetic layer, is formed of the four layers of antiferromagneticlayer/first pinned magnetic layer/nonmagnetic intermediate layer/secondpinned magnetic layer. Thus, the magnetization state of the first pinnedmagnetic layer and second pinned magnetic layer can be maintained at anextremely stable state regarding external magnetic fields, but severalconditions are necessary in order to further improve the magnetizationstability of the first pinned magnetic layer and second pinned magneticlayer.

The first is to increase the exchange coupling magnetic field (exchangeanisotropic magnetic field) generated at the interface between theantiferromagnetic layer and the first pinned magnetic layer. Asdescribed above, the magnetization of the first pinned magnetic layer ispinned in a certain direction by the exchange coupling magnetic field(exchange anisotropic magnetic field) generated at the interface withthe antiferromagnetic layer, but if this exchange coupling magneticfield is weak, the pinned magnetization of the first pinned magneticlayer does not stabilize, and easily changes due to external magneticfields and the like. Accordingly, it is preferable that the exchangecoupling magnetic field (exchange anisotropic magnetic field) generatedat the interface with the antiferromagnetic layer be large. The presentinvention provides a PtMn alloy as an antiferromagnetic layer whereby alarge exchange coupling magnetic field generated at the interface withthe first pinned magnetic layer can be obtained. Also, an X—Mn alloy(wherein X is one or a plurality of the following elements: Pd, Ir, Rh,Ru, and Os), or a PtMn—X′ alloy (wherein X′ is one or a plurality of thefollowing elements: Pd, Ir, Rh, Ru, Os, Au, and Ag) may be used insteadof the PtMn alloy.

These antiferromagnetic materials have excellent properties, as theyproduce a greater exchange coupling magnetic field than NiO, FeMnalloys, NiMn alloys, and the like which are conventionally used forantiferromagnetic materials, have high blocking temperatures, furtherhave excellent corrosion-resistant properties, and so forth.

FIG. 26 shows R-H curves of a spin-valve magnetoresistive thin filmelement according to the present invention wherein the pinned magneticlayer is divided into two layers with a nonmagnetic intermediate layerintroduced therebetween, using a PtMn alloy for the antiferromagneticlayer, and a known spin-valve magnetoresistive thin film element whereinthe pinned magnetic layer is formed as a single layer.

The film configuration of the spin-valve magnetoresistive thin filmelement according to the present invention is: from the bottom; the Sisubstrate/Alumina: Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn(200)/first pinned magnetic layer of Co (25)/nonmagnetic intermediatelayer of Ru (7)/second pinned magnetic layer of Co (20)/Cu (20)/Co(10)/NiFe (40)/Ta (30); wherein the numerals in the parenthesesrepresent film thickness in units of ängström; whereas the filmconfiguration of the known spin-valve magnetoresistive thin film elementis from the bottom; the Si substrate/Alumina: Al₂O₃/Ta(30)/antiferromagnetic layer of PtMn (300)/pinned magnetic layer of Co(25)/Cu (20)/Co (10)/NiFe (40)/Ta (30).

A spin-valve magnetoresistive thin film element according to the presentinvention and a known spin-valve magnetoresistive thin film element wereboth formed, and subjected to thermal treatment at 260° C. for fourhours while applying a magnetic field of 200 (Oe).

As can be understood from FIG. 26, the ΔMR (resistance change rate) ofthe spin-valve magnetoresistive thin film element according to thepresent invention is between 7 to 8% at the greatest, and the ΔMR dropsby applying a negative external magnetic field, but the ΔMR in thepresent invention drops slower than the ΔMR of the known spin-valvemagnetoresistive thin film element.

Now, with the present invention, the magnitude of the external magneticfield at the time that the ΔMR is half of the maximum value shall bestipulated as the exchange coupling magnetic field (Hex) generated bythe spin-valve magnetoresistive thin film element.

As shown in FIG. 26, the maximum ΔMR of the spin-valve magnetoresistivethin film element according to the present invention is approximately8%, and the external magnetic field at which the ΔMR drops to half (theexchange coupling magnetic field (Hex)) is approximately 900 (Oe)absolute value.

In comparison, the maximum ΔMR of the known spin-valve magnetoresistivethin film element is approximately 7.5%, which is slightly lower thanthe known arrangement, the external magnetic field at which the ΔMRdrops to half (the exchange coupling magnetic field (Hex)) isapproximately 2800 (Oe) absolute value, which is much higher.

Thus, it can be understood that the exchange coupling magnetic field(Hex) can be markedly increased with the spin-valve magnetoresistivethin film element according to the present invention wherein the pinnedmagnetic layer is divided into two layers, as compared with the knownspin-valve magnetoresistive thin film element wherein the pinnedmagnetic layer is formed of one layer, and the stability of themagnetization of the pinned magnetic layer can be improved in comparisonwith the known arrangement. Also, the ΔMR of the present invention doesnot drop very much as compared with the known arrangement, showing thata high ΔMR can be maintained.

Next, FIG. 27 is a graph showing the relation between environmentaltemperature and the exchange coupling magnetic field, using four typesof spin-valve magnetoresistive thin film elements.

The first type of spin-valve magnetoresistive thin film element used isa spin-valve magnetoresistive thin film element according to the presentinvention wherein PtMn is used for the antiferromagnetic layer, and thepinned magnetic layer is divided into two layers. The film configurationthereof is from the bottom; the Si substrate/Alumina: Al₂O₃/Ta(30)/antiferromagnetic layer of PtMn (200)/first pinned magnetic layerof Co (25)/nonmagnetic intermediate layer of Ru (7)/second pinnedmagnetic layer of Co (20)/Cu (20)/Co (10)/NiFe (70)/Ta (30).

The second type is a first conventional example wherein a PtMn alloy isused for the antiferromagnetic layer, and the pinned magnetic layer isformed of one layer. The film configuration thereof is from the bottom;the Si substrate/Alumina: Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn(300)/pinned magnetic layer of Co (25)/Cu (25)/Co (10)/NiFe (70)/Ta(30).

The third type is a second conventional example wherein NiO is used forthe antiferromagnetic layer, and the pinned magnetic layer is formed ofone layer. The film configuration thereof is from the bottom; the Sisubstrate/Alumina: Al₂O₃/antiferromagnetic layer of NiO (500)/pinnedmagnetic layer of Co (25)/Cu (25)/Co (10)/NiFe (70)/Ta (30).

The fourth type is a third conventional example wherein a FeMn alloy isused for the antiferromagnetic layer, and the pinned magnetic layer isformed of one layer. The film configuration thereof is from the bottom;the Si substrate/Alumina: Al₂O₃/Ta (30)/NiFe (70)/Co (10)/Cu (25)/pinnedmagnetic layer of Co (25)/antiferromagnetic layer of Femn (150)/Ta (30).In all four types, the numerals in the parentheses represent filmthickness in units of ängström.

The present invention and the first conventional example wherein a PtMnalloy is used for the antiferromagnetic layer are subjected to thermaltreatment at 260° C. for four hours while applying a magnetic field of200 (Oe), following formation. The second and third conventionalexamples wherein NiO and FeMn are used for the antiferromagnetic layerare not subjected to thermal treatment following formation.

As shown in FIG. 27, with the spin-valve magnetoresistive thin filmelement according to the present invention, the exchange couplingmagnetic field (Hex) is approximately 2500 (Oe) under an environmenttemperature of around 200C, which is very high.

In comparison, with the second conventional example using NiO for theantiferromagnetic layer, and the third conventional example using FeMnfor the antiferromagnetic layer, the exchange coupling magnetic field(Hex) is only around 500 (Oe) even under an environment temperature ofaround 20° C., which is low. Also, with the first conventional exampleusing PtMn to form the antiferromagnetic layer, wherein the pinnedmagnetic layer is formed of a single layer, an exchange couplingmagnetic field around 1000 (Oe) is generated under an environmenttemperature of around 200C, so it can be understood that a greaterexchange coupling magnetic field can be obtained than using NiO (secondconventional example) or FeMn (third conventional example) for theantiferromagnetic layer.

U.S. Pat. No. 5,701,223 discloses a spin-valve magnetoresistive thinfilm element which uses NiO for the antiferromagnetic layer, with thepinned magnetic layer being formed of two layers with a nonmagneticintermediate layer introduced therebetween, and the R-H curve thereof isshown in FIG. 8. According to FIG. 8 of the Patent Publication, anexchange coupling magnetic field (Hex) of 600 (Oe) is then to beobtained, but it can be understood that this is low compared to theexchange coupling magnetic field (around 1000 (Oe), first conventionalexample) generated wherein a PtMn alloy is used for theantiferromagnetic layer and the pinned magnetic layer is a single layer.

That is to say, if NiO is used for the antiferromagnetic layer, evendividing the pinned magnetic layer into two layers and placing themagnetization of these two layers in a Ferri-state leaves the exchangecoupling magnetic field lower than an arrangement wherein a PtMn alloyis used for the antiferromagnetic layer and the pinned magnetic layer isa single layer. Consequently, it can be understood that using the PtMnalloy for the antiferromagnetic layer is preferable from the perspectivethat a greater exchange coupling magnetic field can be obtained.

Also, as shown in FIG. 27, in the event that NiO or FeMn alloy is usedfor the antiferromagnetic layer, the exchange coupling magnetic fielddrops to 0 (Oe) once the environment temperature reaches 200° C. This isbecause the blocking temperature of NiO and FeMn alloys is around 200°C., which is low.

Conversely, with the first conventional example wherein the PtMn alloyis used for the antiferromagnetic layer, the exchange coupling magneticfield drops to 0 (Oe) when the environment temperature reaches 400° C.,so it can be understood that using the PtMn, alloy allows themagnetization state of the pinned magnetic layer in an extremely stablecondition, temperature-wise.

The blocking temperature is governed by the material used for theantiferromagnetic layer, so with the spin-valve magnetoresistive thinfilm element according to the present invention shown in FIG. 27, it canbe assumed that the exchange coupling magnetic field drops to 0 (Oe)when the environment temperature reaches 400° C., but with arrangementswhich use PtMn alloys as the antiferromagnetic layer as with the presentinvention, blocking temperatures higher than using NiO or the like canbe obtained, and further, a very large exchange coupling magnetic fieldcan be obtained during the time taken to reach the blocking temperatureby means of dividing the pinned magnetic layer into two layers andplacing the magnetization of these two layers in a Ferri-state, so themagnetization state of the two pinned magnetic layers can be maintainedin an extremely stable condition, temperature-wise.

Also, with the present invention, the nonmagnetic intermediate layerintroduced between the first pinned magnetic layer and second pinnedmagnetic layer is formed of one of the following, or of an alloy of twoor more thereof: Ru, Rh, Ir, Cr, Re, and Cu. The thickness of thenonmagnetic intermediate layer is changed depending on whether theantiferromagnetic layer is formed above the free magnetic layer or belowthe free magnetic layer. The nonmagnetic intermediate layer is formed toa thickness within an appropriate range; whereby the exchange couplingmagnetic field (Hex) can be increased. The appropriate thickness of thenonmagnetic intermediate layer will be described in detail later, withreference to graphs.

Further, according to the present invention, dividing the pinnedmagnetic layer into two layers allows a large exchange coupling magneticfield (Hex) to be obtained even if the antiferromagnetic layer formed ofPtMn alloy or the like is made thinner, meaning that theantiferromagnetic layer which is the thickest layer in the spin-valvemagnetoresistive thin film element configuration can be reduced inthickness, consequently reducing the overall thickness of the spin-valvemagnetoresistive thin film element itself. Reducing the thickness of theantiferromagnetic layer allows the distance from the gap layer formed onthe underside of the spin-valve magnetoresistive thin film element tothe gap layer formed on the upper side of the spin-valvemagnetoresistive thin film element, i.e., the gap length, to be reduced,even if the thicknesses of the gap layers formed above and below thespin-valve magnetoresistive thin film element are formed thick enough tomaintain sufficient insulation, thereby enabling handling of narrowgapping.

Now, if the pinned magnetic layer is divided into a first pinnedmagnetic layer and a second pinned magnetic layer with a nonmagneticintermediate layer introduced therebetween, as with the presentinvention, experimentation has shown that the exchange coupling magneticfield (Hex) and the ΔMR (rate of resistance change) drops drastically inthe event that the first pinned magnetic layer and second pinnedmagnetic layer are formed at the same thicknesses. It is supposed thatthis is due to the fact that forming the first pinned magnetic layer andthe second pinned magnetic layer at the same thickness makes itdifficult to achieve an antiparallel state (Ferri-state) in themagnetization state between the first pinned magnetic layer and thesecond pinned magnetic layer. Since an antiparallel state cannot beachieved between the first pinned magnetic layer and the second pinnedmagnetic layer, the relative angle with the fluctuating magnetization ofthe free magnetic layer cannot be appropriately controlled.

Accordingly, with the present invention, the first pinned magnetic layerand the second pinned magnetic layer are not formed at the samethickness, but rather at differing thicknesses. This allows a largeexchange coupling magnetic field to be obtained, and at the same timeraises the ΔMR to around that of known arrangements. The thickness ratiobetween the first pinned magnetic layer and the second pinned magneticlayer will be described in detail later, with reference to graphs.

As described above, with the present invention, the exchange couplingmagnetic field (Hex) of the entire spin-valve magnetoresistive thin filmelement can be increased by means of dividing the pinned magnetic layerinto a first pinned magnetic layer and a second pinned magnetic layerwith a nonmagnetic intermediate layer introduced therebetween, and byusing an antiferromagnetic material such as a PtMn alloy or the likewhich exhibits a large exchange coupling magnetic field (exchangeanisotropic magnetic field) at the interface with the first pinnedmagnetic layer, as the antiferromagnetic layer. Thus, the magnetizationstate of the first pinned magnetic layer and the second pinned magneticlayer can be maintained in an extremely stable antiparallel state(Ferri-state), temperature-wise.

With the present invention, the exchange coupling magnetic field of theentire spin-valve magnetoresistive thin film element can be increasedand high ΔMR can be obtained, by optimizing the film thickness ratiobetween the divided first pinned magnetic layer and second pinnedmagnetic layer, the material and thickness of the nonmagneticintermediate layer, the thickness of the antiferromagnetic layer, etc.

Spin-valve magnetoresistive thin film elements to which the presentinvention may be applied include both so-called single spin-valvemagnetoresistive thin film elements consisting of one layer each of theantiferromagnetic layer, pinned magnetic layer, nonmagnetic electricallyconductive layer, and free magnetic layer, and so-called dual spin-valvemagnetoresistive thin film elements comprising nonmagnetic electricallyconductive layers, pinned magnetic layers, and antiferromagnetic layersformed above and below with the free magnetic layer as the center.

Further, with the present invention, the free magnetic layer may bedivided into two with the nonmagnetic intermediate layer introducedtherebetween, as with the pinned magnetic layer. The magnetization ofthe first free magnetic layer and second free-magnetic layer formed withthe nonmagnetic intermediate layer introduced therebetween is magnetizedin an antiparallel manner by the exchange coupling magnetic field (RKKYinteraction) generated between the first free magnetic layer and secondfree magnetic layer, and further aligned in a direction intersecting themagnetization of the pinned magnetic layer (first pinned magnetic layerand second pinned magnetic layer).

With the case of the pinned magnetic layer (first pinned magnetic layerand second pinned magnetic layer), the magnetization is pinned in acertain direction by exchange coupling magnetic field (exchangeanisotropic magnetic field) with the antiferromagnetic layer. However,the magnetization of the free magnetic layer is made to freely changeaccording to external magnetic fields, so electric resistance changesdue to the relationship between change in magnetization of the freemagnetic layer and the direction of the pinned magnetization of thepinned magnetic layer, thereby enabling detection of external magneticfield signals.

With the present invention, the antiparallel state (Ferri-state) of thefirst pinned magnetic layer and the second pinned magnetic layer can bemaintained in an extremely stable state temperature-wise, and a high ΔMRas with known arrangements can be obtained, by optimizing the ratio ofthe thickness of the first free magnetic layer and second free magneticlayer divided with the nonmagnetic intermediate layer introducedtherebetween, and the thickness of the nonmagnetic intermediate layer.The ratio of the thickness of the first free magnetic layer and secondfree magnetic layer and the thickness of the nonmagnetic intermediatelayer will be described later in detail with reference to graphs.

Also, a second aspect of the present invention provides a spin-valvemagnetoresistive thin film element, comprising: an antiferromagneticlayer; a pinned magnetic layer formed in a manner contacting theantiferromagnetic layer. The magnetizing direction is pinned by theexchange coupling magnetic field between the pinned magnetic layer andthe antiferromagnetic layer. A nonmagnetic electrically conductive layerformed between a free magnetic layer and the pinned magnetic layer,wherein the magnetizing direction of the free magnetic layer is alignedso as to intersect with the magnetizing direction of the pinned magneticlayer. Electric resistance, which changes according to the relationshipbetween pinned magnetization of the pinned magnetic layer andfluctuating magnetization of the free magnetic layer, is detected bymeans of a sensing current being caused to flow in a directionintersecting the pinned magnetization of the pinned magnetic layer.

The pinned magnetic layer is divided into the two layers of a firstpinned magnetic layer which comes in contact with the antiferromagneticlayer and a second pinned magnetic layer which comes in contact with thenonmagnetic electrically conductive layer, with a nonmagneticintermediate layer introduced therebetween.

The sensing current is caused to flow in a direction such that thedirection of the sensing current magnetic field formed at the firstpinned magnetic layer/nonmagnetic intermediate layer/second pinnedmagnetic layer portion by means of causing the sensing current to flow,and the direction of a synthesized magnetic moment formed by adding themagnetic moment of the first pinned magnetic layer (wherein saturationmagnetization is Ms and film thickness is t) and the magnetic moment ofthe second pinned magnetic layer, are the same direction.

Also, with the present invention, the spin-valve magnetoresistive thinfilm element may be a single spin-valve magnetoresistive thin filmelement consisting of one layer each of the antiferromagnetic layer,first pinned magnetic layer, nonmagnetic intermediate layer, secondpinned magnetic layer, nonmagnetic electrically conductive layer, andfree magnetic layer.

If the magnetic moment of the first pinned magnetic layer is greaterthan the magnetic moment of the second pinned magnetic layer, thesensing current must be caused to flow in a direction such that thedirection of the sensing current magnetic field formed at the firstpinned magnetic layer/nonmagnetic intermediate layer/second pinnedmagnetic layer portion by means of causing the sensing current to flow,and the direction of the magnetic moment of the first pinned magneticlayer, are the same direction or, the spin-valve magnetoresistive thinfilm element may be a single spin-valve magnetoresistive thin filmelement consisting of one layer each of the antiferromagnetic layer,first pinned magnetic layer, nonmagnetic intermediate layer, secondpinned magnetic layer, nonmagnetic electrically conductive layer, andfree magnetic layer.

If the magnetic moment of the first pinned magnetic layer is smallerthan the magnetic moment of the second pinned magnetic layer, thesensing current must be caused to flow in a direction such that thedirection of the sensing current magnetic field formed at the firstpinned magnetic layer/nonmagnetic intermediate layer/second pinnedmagnetic layer portion by means of causing the sensing current to flow,and the direction of the magnetic moment of the second pinned magneticlayer, are the same direction.

Also, with the present invention, the free magnetic layer preferably isdivided into two layers with a nonmagnetic intermediate layer introducedtherebetween. Further, the nonmagnetic intermediate layer introducedbetween the free magnetic layer divided into two layers is preferablyformed of one of the following; or of an alloy of two or more thereof:Ru, Rh, Ir, Cr, Re, and Cu.

Also, according to the present invention, the spin-valvemagnetoresistive thin film element may be a dual spin-valvemagnetoresistive thin film element comprising: nonmagnetic electricallyconductive layers formed above and below with the free magnetic layer asthe center. The three layers of the second pinned magneticlayer/nonmagnetic intermediate layer/first pinned magnetic layer areformed above one of the nonmagnetic electrically conductive layer andbelow the other nonmagnetic electrically conductive layer. Theantiferromagnetic layers are formed above one of the first pinnedmagnetic layers and below the other first pinned magnetic layer. Thesynthesized magnetic moment of the first pinned magnetic layer and thesecond pinned magnetic layer formed to the upper side of the freemagnetic layer, and the synthesized magnetic moment of the first pinnedmagnetic layer and the second pinned magnetic layer formed to the lowerside of the free magnetic layer, are facing in mutually oppositedirections.

The sensing current must be caused to flow in a direction such that thedirection of the sensing current magnetic field formed at the firstpinned magnetic layer/nonmagnetic intermediate layer/second pinnedmagnetic layer portion by causing the sensing current to flow, and thedirection of the synthesized magnetic moment formed above and below thefree magnetic layer, are the same direction.

With regard to specific magnitude of the magnetic moment of the firstpinned magnetic layer and second pinned magnetic layer in theabove-described dual spin-valve magnetoresistive thin film element, itis necessary that the magnetic moment of the first pinned magnetic layerformed to the upper side of the free magnetic layer be greater than themagnetic moment of the second pinned magnetic layer formed to the upperside of the free magnetic layer; and that the magnetic moment of thefirst pinned magnetic layer formed to the lower side of the freemagnetic layer be smaller than the magnetic moment of the second pinnedmagnetic layer formed to the lower side of the free magnetic layer; andfurther that the pinned magnetization of the first pinned magneticlayers formed above and below the free magnetic layer be facing in thesame direction.

Or, it is necessary that the magnetic moment of the first pinnedmagnetic layer formed to the upper side of the free magnetic layer besmaller than the magnetic moment of the second pinned magnetic layerformed to the upper side of the free magnetic layer; and that themagnetic moment of the first pinned magnetic layer formed to the lowerside of the free magnetic layer be greater than the magnetic moment ofthe second pinned magnetic layer formed to the lower side of the freemagnetic layer; and further that the pinned magnetization of the firstpinned magnetic layers formed above and below the free magnetic layer befacing in the same direction.

With the present invention, it is preferable that the antiferromagneticlayer be formed of a PtMn alloy.

Or, the antiferromagnetic layer may be formed of an X—Mn alloy (whereinX is one or a plurality of the following elements: Pd, Ir, Rh, Ru,Os),or a PtMn—X′ alloy (wherein X′ is one or a plurality of the followingelements: Pd, Ir, Rh, Ru, Os, Au, Ag).

Also, with the present invention, it is preferable that the nonmagneticintermediate layer introduced between the first pinned magnetic layerand second pinned magnetic layer be formed of one of the following; orof an alloy of two or more thereof: Ru, Rh, Ir, Cr, Re, and Cu.

Also, a thin film magnetic head according to the present inventioncomprises shield layers formed above and below the above-describedspin-valve magnetoresistive thin film element, with gap layersintroduced therebetween.

With the present invention, the pinned magnetic layer making up thespin-valve magnetoresistive thin film element is divided into twolayers, with a nonmagnetic intermediate layer introduced between thepinned magnetic layers divided into two layers.

The magnetization of the divided two pinned magnetic layers aremagnetized so as to be in an antiparallel state, and also are in aso-called Ferri-state wherein the magnitude of the magnetic moment ofone pinned magnetic layer differs from the magnetic moment of the otherpinned magnetic layer. The exchange coupling magnetic field (RKKYinteraction) generated between the two pinned magnetic layers is verylarge, around 1,000 (Oe) to 5,000 (Oe), so the two pinned magneticlayers are in a very stable state of antiparallel magnetization.

Now, one of the pinned magnetic layers magnetized in the antiparallelstate (Ferri-state) is formed so as to be in contact with theantiferromagnetic layer, and the magnetization of the pinned magneticlayer which is in contact with the antiferromagnetic layer (hereafterreferred to as the “first pinned magnetic layer”) is fixed in thedirection away from a plane facing a recording medium for example (i.e.,the height direction), by the exchange coupling magnetic field (exchangeanisotropic magnetic field) generated at the interface between thepinned magnetic layer and the antiferromagnetic layer. Accordingly, themagnetization of the pinned magnetic layer facing the first pinnedmagnetic layer with a nonmagnetic intermediate layer introducedtherebetween (hereafter referred to as the “second pinned magneticlayer”) is pinned in a state antiparallel with the magnetization of thefirst pinned magnetic layer.

With the present invention, the portion that has been conventionallycomprised of the two layers of the antiferromagnetic layer and pinnedmagnetic layer, is formed of the four layers of antiferromagneticlayer/first pinned magnetic layer/nonmagnetic intermediate layer/second.pinned magnetic layer, whereby the magnetization state of the firstpinned magnetic layer and second pinned magnetic layer can be maintainedat an extremely stable state regarding external magnetic fields.

Now, in recent years, recording density has increased, and accordingly,increase in temperature within the device owing to increase of therevolutions of the recording medium, increase in temperature due toincrease of sensing current, and increase of sensing current magneticfields may make the magnetization state of the first pinned magneticlayer and the second pinned magnetic layer unstable.

The sensing current is caused to flow in a direction intersecting withthe magnetization direction of the first pinned magnetic layer and thesecond pinned magnetic layer (i.e., in the same direction as themagnetization direction in the free magnetic layer, or the oppositedirection), but a sensing current magnetic field is formed by thecorkscrew rule by causing the sensing current to flow, and this sensingcurrent magnetic field intrudes into the first pinned magneticlayer/nonmagnetic intermediate layer/second pinned magnetic layerportion, in the same or opposite magnetization direction as the firstpinned magnetic layer (or second pinned magnetic layer).

As described above, the magnetic moment of the first pinned magneticlayer is formed so as to differ from the magnetic moment of the secondpinned magnetic layer, thereby placing the magnetization of the firstpinned magnetic layer and the second pinned magnetic layer in anantiparallel magnetized state. With the present invention, thedifference in magnitude of the magnetic moment of the first pinnedmagnetic layer and the second pinned magnetic layer is used to cause thesensing current to flow in an appropriate direction, so that themagnetization state of the first pinned magnetic layer and the secondpinned magnetic layer is placed in a thermally more stable state, by thesensing current magnetic field.

Specifically, with the spin-valve magnetoresistive thin film element, ifthe magnetic moment of the first pinned magnetic layer is greater thanthe magnetic moment of the second pinned magnetic layer, the synthesizedmagnetic moment which can be obtained by adding the magnetic moment ofthe first pinned magnetic layer and the magnetic moment of the secondpinned magnetic layer faces the same direction as the magnetic moment ofthe first pinned magnetic layer.

Then, the present invention allows the magnetization state of the firstpinned magnetic layer and the second pinned magnetic layer to be in athermally more stable state, by adjusting the direction of causing thesensing current to flow, so that the sensing current magnetic fieldformed at the portion of the first pinned magnetic layer/nonmagneticintermediate layer/second pinned magnetic layer portion and thedirection of the synthesized magnetic moment match.

Further, with the present invention, a dual spin-valve magnetoresistivethin film element allows the magnetization state of the first pinnedmagnetic layer and the second pinned magnetic layer to be in a thermallystable state, by adjusting the magnetic moment and so forth of the firstpinned magnetic layer and the magnetic moment of the second pinnedmagnetic layer such that the synthesized magnetic moments formed aboveand below the free magnetic layer are mutually opposing, thereby causingthe sensing current to flow such that the sensing current magnetic fieldformed at the portion of the first pinned magnetic layer/nonmagneticintermediate layer/second pinned magnetic layer portion and thedirection of the synthesized magnetic moment match.

Also, according to the present invention, several conditions other thanthe direction of the sensing current are used in order to improve themagnetization stability of the first pinned magnetic layer and secondpinned magnetic layer.

The first is to increase the exchange coupling magnetic field (exchangeanisotropic magnetic field) generated at the interface between theantiferromagnetic layer and the first pinned magnetic layer. Asdescribed above, the magnetization of the first pinned magnetic layer ispinned in a certain direction by the exchange coupling magnetic field(exchange anisotropic magnetic field) generated at the interface withthe antiferromagnetic layer, but if this exchange coupling magneticfield is weak, the pinned magnetization of the first pinned magneticlayer does not stabilize, and easily changes due to external magneticfields and the like. Accordingly, it is preferable that the exchangecoupling magnetic field (exchange anisotropic magnetic field) generatedat the interface with the antiferromagnetic layer be great, and thepresent invention gives a PtMn alloy as an antiferromagnetic layerwhereby a large exchange coupling magnetic field generated at theinterface with the first pinned magnetic layer can be obtained. Also, anX—Mn alloy (wherein X is one or a plurality of the following elements:Pd, Ir, Rh, Ru, and Os), or a PtMn—X′ alloy (wherein X′ is one or aplurality of the following elements: Pd, Ir, Rh, Ru, Os, Au, and Ag) maybe used instead of the PtMn alloy.

These antiferromagnetic materials have excellent properties, as theyproduce a greater exchange coupling magnetic field than NiO, FeMnalloys, NiMn alloys, and the like conventionally used forantiferromagnetic materials, have high blocking temperatures, furtherhave excellent corrosion-resistant properties, and so forth.

FIG. 26 shows R-H curves of the spin-valve magnetoresistive thin filmelement according to the present invention using a PtMn alloy for theantiferromagnetic layer, wherein the pinned magnetic layer is dividedinto two layers with a nonmagnetic intermediate layer introducedtherebetween, and a known spin-valve magnetoresistive thin film elementwherein the pinned magnetic layer is formed as a single layer.

The film configuration of the spin-valve magnetoresistive thin filmelement according to the present invention is: from the bottom; the Sisubstrate/Alumina/Ta (30)/antiferromagnetic layer of PtMn (200)/firstpinned magnetic layer of Co (25)/nonmagnetic intermediate layer of Ru(7)/second pinned magnetic layer of Co (20)/Cu (20)/Co (10)/NiFe (40)/Ta(30); wherein the numerals in the parentheses represent film thicknessin units of Ångström; whereas the film configuration of the knownspin-valve magnetoresistive thin film element is from the bottom; the Sisubstrate/Alumina: Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn(300)/pinned magnetic layer of Co (25)/Cu (20)/Co (10)/NiFe (40)/Ta(30).

A spin-valve magnetoresistive thin film element according to the presentinvention and a known spin-valve magnetoresistive thin film element wereboth formed, and subjected to thermal treatment at 260° C. for fourhours while applying a magnetic field of 200 (Oe).

As can be understood from FIG. 26, the ΔMR (resistance change rate) ofthe spin-valve magnetoresistive thin film element according to thepresent invention is between 7 to 8% at the greatest, and the ΔMR dropsby applying a negative external magnetic field, but the ΔMR in thepresent invention drops slower than the ΔMR of the known spin-valvemagnetoresistive thin film element.

Now, with the present invention, the magnitude of the external magneticfield at the time that the ΔMR is half of the maximum value shall bestipulated as the exchange coupling magnetic field (Hex) generated bythe spin-valve magnetoresistive thin film element.

As shown in FIG. 26, the maximum ΔMR of the known spin valvemagnetoresistive thin film element is approximately 8%, and the externalmagnetic field at which the ΔMR drops to half (the exchange couplingmagnetic field (Hex)) is approximately 900 (Oe) absolute value.

In comparison, with the present invention the maximum ΔMR of the knownspin-valve magnetoresistive thin film element is approximately 7.5%,which is slightly lower than the known arrangement, the externalmagnetic field at which the ΔMR drops to half (the exchange couplingmagnetic field (Hex)) is approximately 2800 (Oe) absolute value, whichis much higher.

Thus, it can be understood that the exchange coupling magnetic field(Hex) can be markedly increased with the spin-valve magnetoresistivethin film element according to the present invention wherein the pinnedmagnetic layer is divided into two layers, as compared with the knownspin-valve magnetoresistive thin film element wherein the pinnedmagnetic layer is formed of one layer, and the stability of themagnetization of the pinned magnetic layer can be improved in comparisonwith the known arrangement. Also, the ΔMR of the present invention doesnot drop very much as compared with the known arrangement, showing thata high ΔMR can be maintained.

Next, FIG. 27 is a graph showing the relation between environmentaltemperature and the exchange coupling magnetic field, using four typesof spin-valve magnetoresistive thin film elements.

The first type of spin-valve magnetoresistive thin film element used isa spin-valve magnetoresistive thin film element according to the presentinvention wherein a PtMn alloy is used for the antiferromagnetic layer,and the pinned magnetic layer is divided into two layers. The filmconfiguration thereof is from the bottom; the Si substrate/Alumina:Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn (200)/first pinnedmagnetic layer of Co (25)/nonmagnetic intermediate layer of Ru(7)/second pinned magnetic layer of Co (20)/Cu (20)/Co (10)/NiFe (70)/Ta(30).

The second type is a first conventional example wherein a PtMn alloy isused for the antiferromagnetic layer, and the pinned magnetic layer isformed of one layer. The film configuration thereof is from the bottom;the Si substrate/Alumina: Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn(300)/pinned magnetic layer of Co (25)/Cu (25)/Co (10)/NiFe (70)/Ta(30).

The third type is a second conventional example wherein NiO is used forthe antiferromagnetic layer, and the pinned magnetic layer is formed ofone layer. The film configuration thereof is from the bottom; the Sisubstrate/Alumina: Al₂ O₃/antiferromagnetic layer of NiO (500)/pinnedmagnetic layer of Co (25)/Cu (25)/Co (10)/NiFe (70)/Ta (30).

The fourth type is a third conventional example wherein an FeMn alloy isused for the antiferromagnetic layer, and the pinned magnetic layer isformed of one layer. The film configuration thereof is from the bottom;the Si substrate/Alumina: Al₂O₃/Ta (30)/NiFe (70)/Co (10)/Cu (25)/pinnedmagnetic layer of Co (25)/antiferromagnetic layer of FeMn (150)/Ta (30).In all four types, the numerals in the parentheses represent filmthickness in units of ängström.

The present invention and the first conventional example wherein a PtMnalloy is used for the antiferromagnetic layer are subjected to thermaltreatment at 260° C. for four hours while applying a magnetic field of200 (Oe), following formation. The second and third conventionalexamples wherein NiO and FeMn are used for the antiferromagnetic layerare not subjected to thermal treatment following formation.

As shown in FIG. 27, with the spin-valve magnetoresistive thin filmelement according to the present invention, the exchange couplingmagnetic field (Hex) is approximately 2,500 (Oe) under an environmenttemperature of around 200° C., which is very high.

In comparison, with the second conventional example using NiO for theantiferromagnetic layer, and the third conventional example using FeMnfor the antiferromagnetic layer, the exchange coupling magnetic field(Hex) is only around 500 (Oe) even under an environment temperature ofaround 20° C., which is low. Also, with the first conventional exampleusing PtMn to form the antiferromagnetic layer, wherein the pinnedmagnetic layer is formed of a single layer, an exchange couplingmagnetic field (Hex) around 1,000 (Oe) is generated under an environmenttemperature of around 200° C., so it can be understood that a greaterexchange coupling magnetic field can be obtained than using NiO (secondconventional example) or FeMn (third conventional example) for theantiferromagnetic layer.

U.S. Pat. No. 5,701,223 discloses a spin-valve magnetoresistive thinfilm element which uses NiO for the antiferromagnetic layer, with thepinned magnetic layer being formed of two layers with a nonmagneticintermediate layer introduced therebetween, and the R-H curve thereof isshown in FIG. 8. According to FIG. 8 of the Patent Publication, anexchange coupling magnetic field (Hex) of 600 (Oe) is then to beobtained, but it can be understood that this is low compared to theexchange coupling magnetic field (around 1000 (Oe), first conventionalexample) generated wherein a PtMn alloy is used for theantiferromagnetic layer and the pinned magnetic layer is a single layer.

That is to say, in the event that NiO is used for the antiferromagneticlayer, even dividing the pinned magnetic layer into two layers andplacing the magnetization of these two layers in a Ferri-state leavesthe exchange coupling magnetic field lower than an arrangement wherein aPtMn alloy is used for the antiferromagnetic layer and the pinnedmagnetic layer is a single layer. Consequently, it can be understoodthat using the PtMn alloy for the antiferromagnetic layer is preferablefrom the perspective that a greater exchange coupling magnetic field canbe obtained.

Also, as shown in FIG. 27, if NiO or FeMn alloy is used for theantiferromagnetic layer, the exchange coupling magnetic field drops to 0(Oe) once the environment temperature reaches 200° C. This is becausethe blocking temperature of NiO and FeMn alloys is around 200° C., whichis low.

Conversely, with the first conventional example wherein the PtMn alloyis used for the antiferromagnetic layer, the exchange coupling magneticfield drops to 0 (Oe) when the environment temperature reaches 400° C.,so it can be understood that using the PtMn alloy allows themagnetization state of the pinned magnetic layer in an extremely stablecondition, temperature-wise.

The blocking temperature is governed by the material used for theantiferromagnetic layer, so with the spin-valve magnetoresistive thinfilm element according to the present invention shown in FIG. 27, it canbe assumed that the exchange coupling magnetic field drops to 0 (Oe)when the environment temperature reaches 400° C., but with arrangementswhich use PtMn alloys as the antiferromagnetic material as with thepresent invention, blocking temperatures higher than using NiO or thelike can be obtained, and further, a very large exchange couplingmagnetic field can be obtained during the time taken to reach theblocking temperature by dividing the pinned magnetic layer into twolayers and placing the magnetization of these two layers in aFerri-state, so the magnetization state of the two pinned magneticlayers can be maintained in a thermally stable condition.

Also, with the present invention, the nonmagnetic intermediate layerintroduced between the first pinned magnetic layer and second pinnedmagnetic layer is formed of one of the following, or of an alloy of twoor more thereof: Ru, Rh, Ir, Cr, Re, and Cu; the thickness of thenonmagnetic intermediate layer is changed depending on whether theantiferromagnetic layer is formed above the free magnetic layer or belowthe free magnetic layer; and the nonmagnetic intermediate layer isformed to a thickness within an appropriate range; whereby the exchangecoupling magnetic field (Hex) can be increased. The appropriatethickness of the nonmagnetic intermediate layer will be described indetail later, with reference to graphs.

Further, according to the present invention, dividing the pinnedmagnetic layer into two layers allows a large exchange coupling magneticfield (Hex) to be obtained even if the antiferromagnetic layer formed ofPtMn alloy or the like is made thinner, meaning that theantiferromagnetic layer which is the thickest layer in the spin-valvemagnetoresistive thin film element configuration can be reduced inthickness, consequently reducing the overall thickness of the spin-valvemagnetoresistive thin film element itself. Reducing the thickness of theantiferromagnetic layer allows the distance from the gap layer formed onthe underside of the spin-valve magnetoresistive thin film element tothe gap layer formed on the upper side of the spin-valvemagnetoresistive thin film element, i.e., the gap length, to be reduced,even if the thicknesses of the gap layers formed above and below thespin-valve magnetoresistive thin film element are formed thick enough tomaintain sufficient insulation, thereby enabling handling of narrowgapping.

Now, in the event that the pinned magnetic layer is divided into a firstpinned magnetic layer and a second pinned magnetic layer with anonmagnetic intermediate layer introduced therebetween, as with thepresent invention, experimentation has shown that the exchange couplingmagnetic field (Hex) and the ΔMR (rate of resistance change) dropsdrastically in the event that the first pinned magnetic layer and secondpinned magnetic layer are formed at the same thicknesses. It is supposedthat this is due to the fact that forming the first pinned magneticlayer and the second pinned magnetic layer at the same thickness makesit difficult to achieve an antiparallel state (Ferri-state) in themagnetization state between the first pinned magnetic layer and thesecond pinned magnetic layer. Since an antiparallel state cannot beachieved between the first pinned magnetic layer and the second pinnedmagnetic layer, the relative angle with the fluctuating magnetization ofthe free magnetic layer cannot be appropriately controlled.

Accordingly, with the present invention, the first pinned magnetic layerand the second pinned magnetic layer are not formed at the samethickness, but rather at differing thicknesses, thereby allowing a largeexchange coupling magnetic field to be obtained, and at the same timeraising the ΔMR to around that of known arrangements. The thicknessratio between the first pinned magnetic layer and the second pinnedmagnetic layer will be described in detail later, with reference tographs.

As described above, with the present invention, the exchange couplingmagnetic field (Hex) of the entire spin-valve magnetoresistive thin filmelement can be increased by dividing the pinned magnetic layer into afirst pinned magnetic layer and a second pinned magnetic layer with anonmagnetic intermediate layer introduced therebetween, and by using anantiferromagnetic material such as a PtMn alloy or the like whichexhibits a large exchange coupling magnetic field (exchange anisotropicmagnetic field) at the interface with the first pinned magnetic layer,as the antiferromagnetic layer, so the magnetization state of the firstpinned magnetic layer and the second pinned magnetic layer can bemaintained in a stable antiparallel state (Ferri-state),temperature-wise.

Particularly, with the present invention, the direction of the sensingcurrent magnetic field formed by the flow of sensing current and thedirection of the synthesized magnetic moment which can be obtained byadding the magnetic moment of the first pinned magnetic layer and themagnetic moment of the second pinned magnetic layer are made to match bycontrolling the direction in which the sensing current is made to flow,so the magnetization state of the first pinned magnetic layer and thesecond pinned magnetic layer can be maintained in an even more thermallystable state.

A third aspect of the present invention is a method for manufacturing asingle spin-valve magnetoresistive thin film element, wherein the thinfilm element comprises: an antiferromagnetic layer; a pinned magneticlayer formed in a manner contacting the antiferromagnetic layer, whereinthe magnetization thereof is pinned in a certain direction by theexchange coupling magnetic field generated at the interface between thepinned magnetic layer and the antiferromagnetic layer by thermaltreatment in a magnetic field; and a magnetic electrically conductivelayer formed between a free magnetic layer and the pinned magneticlayer, wherein the magnetizing direction of the free magnetic layer isaligned so as to intersect with the magnetizing direction of the pinnedmagnetic layer; and wherein the thin film element consists of one layereach of an antiferromagnetic layer, pinned magnetic layer, nonmagneticelectrically conductive layer, and free magnetic layer.

The method comprises the steps of:

a process for forming the magnetic moment of the first pinned magneticlayer (wherein saturation magnetization is Ms and film thickness is t)and the magnetic moment of the second pinned magnetic layer so as todiffer in size, at the time that the pinned magnetic layer is dividedinto the two layers of a first pinned magnetic layer coming into contactwith the antiferromagnetic layer and a second pinned magnetic layercoming into contact with the nonmagnetic electrically conductive layer,with a nonmagnetic intermediate layer introduced therebetween; and

a process wherein, at the time of conducting thermal treatment in amagnetic field following forming the single spin-valve magnetoresistivethin film element, a magnetic field of 100 to 1,000 Oe or a magneticfield of 5 kOe or greater is applied in the direction in which pointingof the magnetization of the first pinned magnetic layer is desired ifthe magnetic moment of the first pinned magnetic layer is. greater thanthe magnetic moment of the second pinned magnetic layer, or, a magneticfield of 100 to 1,000 Oe is applied in the direction opposite to whichpointing of the magnetization of the first pinned magnetic layer isdesired or a magnetic field of 5 kOe or greater is applied in thedirection in which pointing of the magnetization of the first pinnedmagnetic layer is desired if the magnetic moment of the first pinnedmagnetic layer is smaller than the magnetic moment of the second pinnedmagnetic layer. With the present invention, the layers for the singlespin-valve magnetoresistive thin film element may be formed from thebottom in the order of: the antiferromagnetic layer, the first pinnedmagnetic layer, the nonmagnetic intermediate layer, the second pinnedmagnetic layer, the nonmagnetic electrically conductive layer, and thefree magnetic layer, or may be formed from the bottom in the order of:the free magnetic layer, the nonmagnetic electrically conductive layer,the second pinned magnetic layer, the nonmagnetic intermediate layer,the first pinned magnetic layer, and the antiferromagnetic layer.

Also, with the present invention, the free magnetic layer may be dividedinto two layers with a nonmagnetic intermediate layer introducedtherebetween.

Also, the present invention provides a method for manufacturing a dualspin-valve magnetoresistive thin film element, this spin-valvemagnetoresistive thin film element comprising: nonmagnetic electricallyconductive layers formed above and below the free magnetic layer withthe free magnetic layer as the center; pinned magnetic layers formedabove one of the nonmagnetic electrically conductive layers and belowthe other nonmagnetic electrically conductive layer, having themagnetization thereof pinned in one direction; and antiferromagneticlayers formed above one of the pinned magnetic layer and below the otherpinned magnetic layer.

The method comprises the steps of:

a process for creating difference in divided pinned magnetic layersformed above and below the free magnetic layer at the time of dividingthe pinned magnetic layer into the two layers of a first pinned magneticlayer coming into contact with the antiferromagnetic layer and a secondpinned magnetic layer coming into contact with the nonmagneticelectrically conductive layer, with the nonmagnetic intermediate layerintroduced therebetween, such that the magnetic moment of the firstpinned magnetic layer (wherein saturation magnetization is Ms and filmthickness is t) formed to the upper side of the free magnetic layer isgreater than the magnetic moment of the second pinned magnetic layerformed to the upper side of the free magnetic layer, and also so thatthe magnetic moment of the first pinned magnetic layer formed to thelower side of the free magnetic layer is smaller than the magneticmoment of the second pinned magnetic layer formed to the lower side ofthe free magnetic layer, or, such that the magnetic moment of the firstpinned magnetic layer formed to the upper side of the free magneticlayer is smaller than the magnetic moment of the second pinned magneticlayer formed to the upper side of the free magnetic layer, and also sothat the magnetic moment of the first pinned magnetic layer formed tothe lower side of the free magnetic layer is greater than the magneticmoment of the second pinned magnetic layer formed to the lower side ofthe free magnetic layer; and

a process for applying a magnetic field of 5 kOe or greater in thedirection in which pointing of the magnetization of the first pinnedmagnetic layer is desired, at the time of generating the exchangecoupling magnetic field generated at the interface between the firstpinned magnetic layer and the antiferromagnetic layer formed above andbelow the free magnetic layer, by thermal treatment in a magnetic fieldfollowing formation of the films of the dual spin-valve magnetoresistivethin film element, thereby pinning the magnetization of both firstpinned magnetic layers in the same direction.

Also, the present invention may be arranged such that the magneticmoment of the first pinned magnetic layer formed to the upper side ofthe free magnetic layer is made to be greater than the magnetic momentof the second pinned magnetic layer formed to the upper side of the freemagnetic layer, and also the magnetic moment of the first pinnedmagnetic layer formed to the lower side of the free magnetic layer ismade to be greater than the magnetic moment of the second pinnedmagnetic layer formed to the lower side of the free magnetic layer, anda magnetic field of 100 to 1,000 Oe or a magnetic field of 5 kOe orgreater is applied in the direction in which pointing of themagnetization of the first pinned magnetic layer is desired, or, suchthat the magnetic moment of the first pinned magnetic layer formed tothe upper side of the free magnetic layer is made to be smaller than themagnetic moment of the second pinned magnetic layer formed to the upperside of the free magnetic layer, and also the magnetic moment of thefirst pinned magnetic layer formed to the lower side of the freemagnetic layer is made to be smaller than the magnetic moment of thesecond pinned magnetic layer formed to the lower side of the freemagnetic layer, and a magnetic field of 100 to 1,000 Oe is applied inthe direction opposite to which pointing of the magnetization of thefirst pinned magnetic layer is desired, or a magnetic field of 5 kOe orgreater is applied in the direction in which pointing of themagnetization of the first pinned magnetic layer is desired, therebypinning the magnetization of both first pinned magnetic layers formedabove and below the free magnetic layer in the same direction.

Further, the present invention provides another method for manufacturinga dual spin-valve magnetoresistive thin film element, this spin-valvemagnetoresistive thin film element comprising: nonmagnetic electricallyconductive layers formed above and below the free magnetic layer withthe free magnetic layer as the center; pinned magnetic layers formedabove one of the nonmagnetic electrically conductive layers and belowthe other nonmagnetic electrically conductive layer, having themagnetization thereof pinned in one direction; and antiferromagneticlayers formed above one of the pinned magnetic layer and below the otherpinned magnetic layer.

The method comprises the steps of:

a process for dividing the free magnetic layer into the two layers of afirst free magnetic layer and a second free magnetic layer with anonmagnetic intermediate layer introduced therebetween, and aligning themagnetization of the first pinned magnetic layer and the magnetizationof the second pinned magnetic layer in an antiparallel manner;

a process for creating difference in divided pinned magnetic layers atthe time of dividing the pinned magnetic layer into the two layers of afirst pinned magnetic layer and a second pinned magnetic layer, with thenonmagnetic intermediate layer introduced therebetween, such that themagnetic moment of the first pinned magnetic layer (wherein saturationmagnetization is Ms and film thickness is t) formed to the upper side ofthe free magnetic layer is greater than the magnetic moment of thesecond pinned magnetic layer formed to the upper side of the freemagnetic layer, and also so that the magnetic moment of the first pinnedmagnetic layer (wherein saturation magnetization is Ms and filmthickness is t) formed to the lower side of the free magnetic layer issmaller than the magnetic moment of the second pinned magnetic layer(wherein saturation magnetization is Ms and film thickness is t) formedto the lower side of the free magnetic layer, or, such that the magneticmoment of the first pinned magnetic layer formed to the upper side ofthe free magnetic layer is smaller than the magnetic moment of thesecond pinned magnetic layer formed to the upper side of the freemagnetic layer, and al so so that the magnetic moment of the firstpinned magnetic layer formed to the lower side of the free magneticlayer is greater th a n the magnetic moment of the second pinnedmagnetic layer formed to the lower side of the free magnetic layer; and

a process for applying a magnetic field of 100 to 1,000 Oe in thedirection in which pointing of the magnetization of the first pinnedmagnetic layer is desired, at the time of generating an exchangecoupling magnetic field at the interface between the first pinnedmagnetic layer and the antiferromagnetic layer formed above and belowthe free magnetic layer, by thermal treatment in a magnetic fieldfollowing forming the dual spin-valve magnetoresistive thin filmelement, thereby aligning and pinning the magnetization of the firstpinned magnetic layers formed above and below the free magnetic layer inan antiparallel manner.

Also, with the present invention, the antiferromagnetic layer ispreferably formed of a PtMn alloy. Further, the antiferromagnetic layermay be formed of an X—Mn alloy (wherein X is one or a plurality of thefollowing elements: Pd, Ir, Rh, Ru, Os), or a PtMn—X′ alloy (wherein X′,is one or a plurality of the following elements: Pd, Ir, Rh, Ru, Os, Au,Ag), instead of the PtMn alloy.

Further, according to the present invention, the nonmagneticintermediate layer introduced between the first pinned magnetic layerand second pinned magnetic layer, and the nonmagnetic intermediate layerintroduced between the first free magnetic layer and second freemagnetic layer, are preferably formed of one of the following; or of analloy of two or more thereof: Ru, Rh, Ir, Cr, Re, and Cu.

Also, the present invention is a method for manufacturing a thin filmmagnetic head, the head comprising: the above-described spin-valvemagnetoresistive thin film element formed above a lower shield layerwith a gap layer introduced therebetween; and an upper shield layerformed above the spin-valve magnetoresistive thin film element, with agap layer introduced therebetween.

With the present invention, the pinned magnetic layer making up thespin-valve magnetoresistive thin film element is divided into twolayers, with a nonmagnetic intermediate layer introduced between thepinned magnetic layers divided into two layers.

The magnetization of the two divided pinned magnetic layers aremagnetized so as to be in an antiparallel state, and also are in aso-called Ferri-state wherein the magnitude of the magnetic moment ofone pinned magnetic layer differs from the magnetic moment of the otherpinned magnetic layer. The exchange coupling magnetic field (RKKYinteraction) generated between the two pinned magnetic layers is verylarge, around 1,000 (Oe) to 5,000 (Oe), so the two pinned magneticlayers are in a very stable state of antiparallel magnetization.

Now, one of the pinned magnetic layers magnetized in the antiparallelstate (Ferri-state) is formed so as to be in contact with theantiferromagnetic layer, and the magnetization of the pinned magneticlayer which is in contact with the antiferromagnetic layer (hereafterreferred to as the “first pinned magnetic layer”) is pinned in thedirection away from a plane facing a recording medium for example (i.e.,the height direction), by the exchange coupling magnetic field (exchangeanisotropic magnetic field) generated at the interface between thepinned magnetic layer and the antiferromagnetic layer. Accordingly, themagnetization of the pinned magnetic layer facing the first pinnedmagnetic layer with a nonmagnetic intermediate layer introducedtherebetween (hereafter referred to as the “second pinned magneticlayer”) is pinned in a state antiparallel with the magnetization of thefirst pinned magnetic layer.

With the present invention, the portion that has been conventionallycomprised of the two layers of the antiferromagnetic layer and pinnedmagnetic layer, is formed of the four layers of antiferromagneticlayer/first pinned magnetic layer/nonmagnetic intermediate layer/secondpinned magnetic layer, whereby the magnetization state of the firstpinned magnetic layer and second pinned magnetic layer can be maintainedat an extremely stable state regarding external magnetic fields.Particularly, in cases such as with the present invention whereinantiferromagnetic material is used for generating an exchange couplingmagnetic field (exchange anisotropic magnetic field) at the interfacebetween the first pinned magnetic layer and the antiferromagnetic layerby performing thermal treatment in a magnetic field, the direction andmagnitude of the magnetic field during thermal treatment must becontrolled appropriately, or the magnetization of the first pinnedmagnetic layer and second pinned magnetic layer cannot be maintained inan antiparallel state.

Also, a problem that arises regarding the magnetization control of thefirst pinned magnetic layer and second pinned magnetic layer is therelationship between the fluctuating magnetization of the free magneticlayer and the pinned magnetization of the second pinned magnetic layerformed above and below the free magnetic layer, in the case of dualspin-valve magnetoresistive thin film elements.

With dual spin-valve magnetoresistive thin film elements, nonmagneticelectrically conductive layers and pinned magnetic layers are formedabove and below the free magnetic layer, so a greater ΔMR (the rate ofresistance change) can be expected as compared to single spin-valvemagnetoresistive thin film elements. However, the rate of resistancechange according to the relationship between the fluctuatingmagnetization of the free magnetic layer, and the second pinned magneticlayer formed above the free magnetic layer with a nonmagneticelectrically conductive layer introduced therebetween; and the rate ofresistance change according to the relationship between the fluctuatingmagnetization of the free magnetic layer, and the second pinned magneticlayer formed below the free magnetic layer with a nonmagneticelectrically conductive layer introduced therebetween; must both exhibitthe same fluctuation, and the direction of pinned magnetization of thesecond pinned magnetic layer must be appropriately controlled to thisend.

That is, the direction of pinned magnetization of the second pinnedmagnetic layer must be appropriately controlled so that in the eventthat the rate of resistance change at the upper side of the freemagnetic layer is maximum, the rate of resistance change at the lowerside of the free magnetic layer must also be made to be maximum, and inthe event that the rate of resistance change at the upper side of thefree magnetic layer is minimum, the rate of resistance change at thelower side of the free magnetic layer must also be made to be minimum.

Accordingly, with the present invention, the magnitude of the values ofmagnetic moment at the first pinned magnetic layer and magnetic momentat the second pinned magnetic layer are appropriately adjusted, alongwith adjusting the size and direction of the magnetic field appliedduring thermal treatment, thereby appropriately controlling the pinnedmagnetization direction of the first pinned magnetic layer and thepinned magnetization direction of the second pinned magnetic layer.

Next, with reference to FIG. 21, the difference between a spin-valvemagnetoresistive thin film element according to the present inventionwherein the pinned magnetic layer is divided into a first pinnedmagnetic layer and second pinned magnetic layer, and a known hysteresisloop wherein the pinned magnetic layer is formed of a single layer, willbe described.

FIG. 26 shows R-H curves of the spin-valve magnetoresistive thin filmelement according to the present invention, wherein a PtMn alloy is usedas the antiferromagnetic layer and the pinned magnetic layer is dividedinto the two layers of the first pinned magnetic layer and second pinnedmagnetic layer with a nonmagnetic intermediate layer introducedtherebetween, and a known spin-valve magnetoresistive thin film element,wherein the pinned magnetic layer is formed as a single layer.

The film configuration of the spin-valve magnetoresistive thin filmelement according to the present invention is: from the bottom; the Sisubstrate/Alumina/Ta (30)/antiferromagnetic layer of PtMn (200)/firstpinned magnetic layer of Co (25)/nonmagnetic intermediate layer of Ru(7)/second pinned magnetic layer of Co (20)/Cu (20)/Co (10)/NiFe (40)/Ta(30); wherein the numerals in the parentheses represent film thicknessin units of ängström whereas the film configuration of the knownspin-valve magnetoresistive thin film element is from the bottom; the Sisubstrate/Alumina: Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn (300)pinned magnetic layer of Co (25)/Cu (20)/Co (10)/NiFe (40)/Ta (30).

A spin-valve magnetoresistive thin film element according to the presentinvention and a known spin-valve magnetoresistive thin film element wereboth formed, and subjected to thermal treatment at 260° C. for fourhours while applying a magnetic field of 200 (Oe).

As can be understood from FIG. 26, the ΔMR (resistance change rate) ofthe spin-valve magnetoresistive thin film element according to thepresent invention is between 7 to 8% at the greatest, and the ΔMR dropsby applying a negative external magnetic field, but the ΔMR in thepresent invention drops slower than the ΔMR of the known spin-valvemagnetoresistive thin film element.

Now, with the present invention, the magnitude of the external magneticfield at the time that the ΔMR is half of the maximum value shall bestipulated as the exchange coupling magnetic field (Hex) generated bythe spin-valve magnetoresistive thin film element.

As shown in FIG. 26, the maximum ΔMR of the known spin valvemagnetoresistive thin film element is approximately 8%. Further, theexternal magnetic field at which the ΔMR drops to half (the exchangecoupling magnetic field (Hex)) is approximately 900 (Oe) absolute value.

In comparison, the maximum ΔMR of the spin-valve magnetoresistive thinfilm element according to the present invention is approximately 7.5%,which is slightly lower than the known arrangement, the externalmagnetic field at which the ΔMR drops to half (the exchange couplingmagnetic field (Hex)) is approximately 2800 (Oe) absolute value, whichis much higher.

Thus, it can be understood that the exchange coupling magnetic field(Hex) can be markedly increased with the spin-valve magnetoresistivethin film element according to the present invention wherein the pinnedmagnetic layer is divided into two layers, as compared with the knownspin-valve magnetoresistive thin film element wherein the pinnedmagnetic layer is formed of one layer, and the stability of themagnetization of the pinned magnetic layer can be improved in comparisonwith the known arrangement.

Also, the ΔMR of the present invention does not drop very much ascompared with the known arrangement, showing that a high ΔMR can bemaintained.

Also, with the present invention, an antiferromagnetic material whichrequires thermal treatment is used for generating an exchange couplingmagnetic field (exchange anisotropic magnetic field) at the interfacebetween the first pinned magnetic layer and the antiferromagnetic layer,and with the present invention in particular, PtMn alloys are preferablyused of all the antiferromagnetic materials which require thermaltreatment.

FIG. 27 is a graph showing the relation between environmentaltemperature and the exchange coupling magnetic field, in cases whereinthe antiferromagnetic layer is formed of PtMn, NiO, or FeMn.

The first type of spin-valve magnetoresistive thin film element used isa spin-valve magnetoresistive thin film element according to the presentinvention wherein a PtMn alloy is used for the antiferromagnetic layer,and the pinned magnetic layer is divided into two layers. The filmconfiguration thereof is from the bottom; the Si substrate/Alumina:Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn (200)/first pinnedmagnetic layer of Co (25)/nonmagnetic intermediate layer of Ru(7)/second pinned magnetic layer of Co (20)/Cu (20)/Co (10)/NiFe (70)/Ta(30).

The second type is a first conventional example wherein a PtMn alloy isused for the antiferromagnetic layer, and the pinned magnetic layer isformed of one layer. The film configuration thereof is from the bottom;the Si substrate/Alumina: Al₂O₃/Ta (30)/antiferromagnetic layer of PtMn(300)/pinned magnetic layer of Co (25)/Cu (25)/Co (10)/NiFe (70)/Ta(30).

The third type is a second conventional example wherein NiO is used forthe antiferromagnetic layer, and the pinned magnetic layer is formed ofone layer. The film configuration thereof is from the bottom; the Sisubstrate/Alumina: Al₂O₃/antiferromagnetic layer of NiO (500)/pinnedmagnetic layer of Co (25)/Cu (25)/Co (10)/NiFe (70)/Ta (30).

The fourth type is a third conventional example wherein an FeMn alloy isused for the antiferromagnetic layer, and the pinned magnetic layer isformed of one layer. The film configuration thereof is from the bottom;the Si substrate/Alumina: Al₂O₃/Ta (30)/NiFe (70)/Co (10)/Cu (25)/pinnedmagnetic layer of Co (25)/antiferromagnetic layer of FeMn (150)/Ta (30).In all four types, the numerals in the parentheses represent filmthickness in units of ängström.

The present invention and the first conventional example wherein a PtMnalloy is used for the antiferromagnetic layer are subjected to thermaltreatment at 260° C. for four hours while applying a magnetic field of200 (Oe), following formation. The second and third conventionalexamples wherein NiO and FeMn are used for the antiferromagnetic layerare not subjected to thermal treatment following formation.

As shown in FIG. 27, with the spin-valve magnetoresistive thin filmelement according to the present invention, the exchange couplingmagnetic field (Hex) is approximately 2500 (Oe) under an environmenttemperature of around 20° C., which is very high.

In comparison, with the second conventional example using NiO for theantiferromagnetic layer, and the third conventional example using FeMnfor the antiferromagnetic layer, the exchange coupling magnetic field(Hex) is only around 500 (Oe) even under an environment temperature ofaround 20° C., which is low. Also, with the first conventional exampleusing PtMn to form the antiferromagnetic layer, wherein the pinnedmagnetic layer is formed of a single layer, an exchange couplingmagnetic field around 1000 (Oe) is generated under an environmenttemperature of around 20° C., so it can be understood that a greaterexchange coupling magnetic field can be obtained than using NiO (secondconventional example) or FeMn (third conventional example) for theantiferromagnetic layer.

Japanese Unexamined Patent Publication No. 9-16920 discloses aspin-valve magnetoresistive thin film element which uses NiO for theantiferromagnetic layer, with the pinned magnetic layer being formed oftwo layers with a nonmagnetic intermediate layer introducedtherebetween, and the R-H curve thereof is shown in FIG. 8 of the PatentPublication. According to FIG. 8 of the Patent Publication, an exchangecoupling magnetic field (Hex) of 600 (Oe) is then to be obtained, but itcan be understood that this is low compared to the exchange couplingmagnetic field (around 1000 (Oe), first conventional example) generatedwherein a PtMn alloy is used for the antiferromagnetic layer and thepinned magnetic layer is a single layer.

That is to say, in the event that NiO is used for the antiferromagneticlayer, even dividing the pinned magnetic layer into two layers andplacing the magnetization of these two layers in a Ferri-state leavesthe exchange coupling magnetic field lower than an arrangement wherein aPtMn alloy is used for the antiferromagnetic layer and the pinnedmagnetic layer is a single layer. Consequently, it can be understoodthat using the PtMn alloy for the antiferromagnetic layer is preferablefrom the perspective that a greater exchange coupling magnetic field canbe obtained.

Also, as shown in FIG. 27, in the event that NiO or FeMn alloy is usedfor the antiferromagnetic layer, the exchange coupling magnetic fielddrops to 0 (Oe) once the environment temperature reaches 200° C. This isbecause the blocking temperature of NiO and FeMn alloys is around 200°C., which is low.

Conversely, with the first conventional example wherein the PtMn alloyis used for the antiferromagnetic layer, the exchange coupling magneticfield drops to 0 (Oe) when the environment temperature reaches 400° C.,so it can be understood that using the PtMn alloy allows themagnetization state of the pinned magnetic layer in an extremely stablecondition, temperature-wise.

The blocking temperature is governed by the material used for theantiferromagnetic layer, so with the spin-valve magnetoresistive thinfilm element according to the present invention shown in FIG. 27, it canbe assumed that the exchange coupling magnetic field drops to 0 (Oe)when the environment temperature reaches 400° C., but with arrangementswhich use PtMn alloys as antiferromagnetic layers as with the presentinvention, blocking temperatures higher than using NiO or the like canbe obtained, and further, a very large exchange coupling magnetic fieldcan be obtained during the time taken to reach the blocking temperatureby means of dividing the pinned magnetic layer into two layers andplacing the magnetization of these two layers in a Ferri-state, so themagnetization state of the two pinned magnetic layers can be maintainedin a thermally stable condition.

Also, regarding antiferromagnetic materials which require thermaltreatment that can be used instead of PtMn alloys for generating anexchange coupling magnetic field at the interface between the firstpinned magnetic layer and the antiferromagnetic layer, the presentinvention can propose the following: X—Mn alloys (wherein X is one or aplurality of the following elements: Pd, Ir, Rh, Ru, Os), or PtMn—X′alloys (wherein X′ is one or a plurality of the following elements: Pd,Ir, Rh, Ru, Os, Au, Ag).

As described above, with the present invention, the exchange couplingmagnetic field (Hex) of the entire spin-valve magnetoresistive thin filmelement can be increased by means of dividing the pinned magnetic layerinto a first pinned magnetic layer and a second pinned magnetic layerwith a nonmagnetic intermediate layer introduced therebetween, and byfurther using an antiferromagnetic material such as a PtMn alloy or thelike which exhibits a large exchange coupling magnetic field (exchangeanisotropic magnetic field) at the interface with the first pinnedmagnetic layer, as the antiferromagnetic layer, so the magnetizationstate of the first pinned magnetic layer and the second pinned magneticlayer can be maintained in a stable antiparallel state (Ferri-state),temperature-wise.

Particularly, with the present invention, the magnitude of magneticmoment at the first pinned magnetic layer and at the second pinnedmagnetic layer are appropriately controlled, along with controlling thesize and direction of the magnetic field applied during thermaltreatment, so the magnetization of the first pinned magnetic layer andthe second pinned magnetic layer can be maintained in a thermally stableantiparallel state, and the magnetization of the first pinned magneticlayer and the magnetization of the second pinned magnetic layer can beeasily directed in the desired direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of a spin-valve magnetoresistivethin film element according to a first embodiment of the presentinvention;

FIG. 2 is a cross-sectional view of the spin-valve magnetoresistive thinfilm element shown in FIG. 1, viewed from the side facing the recordingmedium;

FIG. 3 is a side cross-sectional view of a spin-valve magnetoresistivethin film element according to a second embodiment of the presentinvention;

FIG. 4 is a cross-sectional view of the spin-valve magnetoresistive thinfilm element shown in FIG. 3, viewed from the side facing the recordingmedium;

FIG. 5 is a side cross-sectional view of a spin-valve magnetoresistivethin film element according to a third embodiment of the presentinvention;

FIG. 6 is a cross-sectional view of the spin-valve magnetoresistive thinfilm element shown in FIG. 5, viewed from the side facing the recordingmedium;

FIG. 7 is a side cross-sectional view of a spin-valve magnetoresistivethin film element according to a fourth embodiment of the presentinvention;

FIG. 8 is a cross-sectional view of the spin-valve magnetoresistive thinfilm element shown in FIG. 7, viewed from the side facing the recordingmedium;

FIG. 9 is a side cross-sectional view of a spin-valve magnetoresistivethin film element according to a fifth embodiment of the presentinvention;

FIG. 10 is a cross-sectional view of the spin-valve magnetoresistivethin film element shown in FIG. 9, viewed from the side facing therecording medium;

FIG. 11 is a side cross-sectional view of a spin-valve magnetoresistivethin film element according to a sixth embodiment of the presentinvention;

FIG. 12 is a cross-sectional view of the spin-valve magnetoresistivethin film element shown in FIG. 11, viewed from the side facing therecording medium;

FIG. 13 is a cross-sectional view of a recording head (reproducinghead), viewed from the side facing the recording medium;

FIG. 14 is a graph illustrating the relationship between the thicknessof a second pinned magnetic layer (P2) in the event that the thicknessof a first pinned magnetic layer (P1) is fixed at 20 or 40 ängström, andthe exchange coupling magnetic field, and also the relationship between(the thickness of the first pinned magnetic layer (P1))/(the thicknessof the second pinned magnetic layer (P2)) and the exchange couplingmagnetic field (Hex);

FIG. 15 is a graph illustrating the relationship between the thicknessof the second pinned magnetic layer (P2) in the event that the thicknessof the first pinned magnetic layer (P1) is fixed at 20 or 40 ängström,and ΔMR;

FIG. 16 is a graph illustrating the relationship between the thicknessof the first pinned magnetic layer (P1) in the event that the secondpinned magnetic layer (P2) is fixed at 30 ängström, and the exchangecoupling magnetic field, and also the relationship between (thethickness of the first pinned magnetic layer (P1))/(the thickness of thesecond pinned magnetic layer (P2)) and the exchange coupling magneticfield (Hex);

FIG. 17 is a graph illustrating the relationship between the thicknessof the first pinned magnetic layer (P1) in the event that the secondpinned magnetic layer (P2) is fixed at 30 ängström, and ΔMR (%);

FIG. 18 is a graph illustrating, with regard to a dual spin-valvemagnetoresistive thin film element, the relationship between thethicknesses of a first pinned magnetic layer (upper) and first pinnedmagnetic layer (lower), and the exchange coupling magnetic field (Hex);and further, the relationship between (the thickness of the first pinnedmagnetic layer (P1 upper))/(the thickness of the second pinned magneticlayer (P2 upper)) and (the thickness of the first magnetic layer (P1lower))/(the thickness of the second pinned magnetic layer (P2 lower)),and the exchange coupling magnetic field (Hex);

FIG. 19 is a graph illustrating the relationship between the thicknessof the Ru (nonmagnetic intermediate layer) introduced between the firstpinned magnetic layer and second pinned magnetic layer, and the exchangecoupling magnetic field (Hex);

FIG. 20 is a graph illustrating, with regard to four types of spin-valvemagnetoresistive thin film elements, the relationship between thethickness of the PtMn (antiferromagnetic layer) of each spin-valvemagnetoresistive thin film element, and the exchange coupling magneticfield (Hex);

FIG. 21 is a graph illustrating, with regard to two types of dualspin-valve magnetoresistive thin film elements, the relationship betweenthe thickness of the PtMn (antiferromagnetic layer) of each dualspin-valve magnetoresistive thin film element, and the exchange couplingmagnetic field (Hex);

FIG. 22 is a graph illustrating, with regard to two types of dualspin-valve magnetoresistive thin film elements, the relationship betweenthe thickness of the PtMn (antiferromagnetic layer) of each dualspin-valve magnetoresistive thin film element, and the ΔMR (%);

FIG. 23 is a graph illustrating the relationship between the thicknessof the second free magnetic layer (F2) in the event that the thicknessof the first free magnetic layer (F1) is fixed at 50 ängström, and theexchange coupling magnetic field (Hex), and also the relationshipbetween (the thickness of the first free magnetic layer (F1))/(thethickness of the second free magnetic layer (F2)) and the exchangecoupling magnetic field (Hex);

FIG. 24 is a graph illustrating the relationship between the thicknessof the first free magnetic layer (F1) in the event that the thickness ofthe second free magnetic layer (F2) is fixed at 20 ängström, and ΔMR(%); and also the relationship between (the thickness of the first freemagnetic layer (F1))/(the thickness of the second free magnetic layer(F2)), and ΔMR (%);

FIG. 25 is a graph illustrating the relationship between the thicknessof the Ru (nonmagnetic intermediate layer) introduced between the firstfree magnetic layer (F1) and second free magnetic layer (F2), and theexchange coupling magnetic field (Hex);

FIG. 26 illustrates the hysteresis loop of a spin-valve magnetoresistivethin film element according to the present invention, and a knownspin-valve magnetoresistive thin film element;

FIG. 27 is a graph illustrating the relationship between environmenttemperature (° C.) and exchange coupling magnetic field (Hex) forseveral spin-valve magnetoresistive thin film elements, wherein theantiferromagnetic layer for one is formed of PtMn, another of NiO, andyet another of FeMn;

FIG. 28 is a cross-sectional view of a known spin-valve magnetoresistivethin film element, viewed from the side facing the recording medium; and

FIG. 29 is a side cross-sectional view of the spin valvemagnetoresistive thin film element shown in FIG. 28.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a side cross-sectional view schematically showing a spin-valvemagnetoresistive thin film element according to a first embodiment ofthe present invention, and FIG. 2 is a cross-sectional view of thespin-valve magnetoresistive thin film element shown in FIG. 1, viewedfrom the side facing the recording medium.

Shield layers are formed above and below this spin valvemagnetoresistive thin film element, with gap layers introducedtherebetween. A reproducing thin film magnetoresistive head (MR head)comprises the spin-valve magnetoresistive thin film element, gap layers,and shield layers. Further, an inductive head for recording may belayered upon the reproducing thin film magnetoresistive head.

This thin film magnetoresistive head is provided to the trailing edge orthe like of a floating slider provided in a hard disk drive, and detectsrecorded magnetic fields on the hard disk or the like. Here, thedirection of motion of the magnetic recording medium such as a hard diskis in the Z direction as shown in the Figure, and the direction ofleaking magnetic field from the magnetic recording medium is in the Ydirection.

The spin-valve magnetoresistive thin film element shown in FIGS. 1 and 2are single spin-valve magnetoresistive thin film elements, consisting ofone layer each of antiferromagnetic layer, pinned magnetic layer,nonmagnetic electrically conductive layer, and free magnetic layer. Thelayer formed at the very bottom is a base layer 10 formed of nonmagneticmaterial such as Ta. In FIGS. 1 and 2, an antiferromagnetic layer 11 isformed on the base layer 10, and a first pinned magnetic layer 12 isformed on the antiferromagnetic layer 11. Then, as shown in FIG. 1, anonmagnetic intermediate layer 13 is formed on the first pinned magneticlayer 12, and further, a second pinned magnetic layer 14 is formed onthe nonmagnetic intermediate layer 13.

The first pinned magnetic layer 12 and second pinned magnetic layer 14are formed of, e.g., Co film, NiFe alloy, Co—NiFe alloy, Co—Fe alloy, orthe like.

Also, with the present invention, it is preferable that theantiferromagnetic layer 11 be formed of a PtMn alloy. PtMn alloys havebetter corrosion-resistant properties than NiMn alloys or FeMn alloysconventionally used for antiferromagnetic layers, the blockingtemperature is high, and a large exchange coupling magnetic field(exchange anisotropic magnetic field) can be obtained. Also, with thepresent invention, X—Mn alloys (wherein X is one or a plurality of thefollowing elements: Pd, Ir, Rh, Ru, Os) or PtMn—X′ alloys (wherein X′,is one or a plurality of the following elements: Pd, Ir, Rh, Ru, Os, Au,Ag) may be used instead of PtMn alloys.

Now, the arrows shown in FIG. 1 for the first pinned magnetic layer 12and second pinned magnetic layer 14 represent the magnitude anddirection of the magnetic moment of each, the magnitude of the magneticmoment being determined by a value obtained by multiplying saturatedmagnetization (Ms) and film thickness (t).

The first pinned magnetic layer 12 and second pinned magnetic layer 14shown in FIG. 1 are formed of the same material, Co film for example,and the thickness t_(P2) of the second pinned magnetic layer 14 isformed so as to be greater than the thickness t_(P1), of the firstpinned magnetic layer 12, so the second pinned magnetic layer 14 has agreater magnetic moment that the first pinned magnetic layer 12. Thepresent invention requires that first pinned magnetic layer 12 and thesecond pinned magnetic layer 14 have different magnetic moments, soalternatively the thickness t_(P1) of the first pinned magnetic layer 12may be formed so as to be greater than the thickness t_(P2), of thesecond pinned magnetic layer 14.

As shown in FIG. 1, the first pinned magnetic layer 12 is magnetized inthe Y direction in the Figure, i.e., in the direction away from therecording medium (the height direction), and the magnetization of thesecond pinned magnetic layer 14 which faces the first pinned magneticlayer 12 with the nonmagnetic intermediate layer 13 introducedtherebetween is magnetized in a manner antiparallel to the first pinnedmagnetic layer 12.

The first pinned magnetic layer 12 is formed so as to come into contactwith the antiferromagnetic layer 11, and annealing (thermal treatment)in a magnetic field causes an exchange coupling magnetic field (exchangeanisotropic magnetic field) to be generated at the interface between thefirst pinned magnetic layer 12 and the antiferromagnetic layer 11, sothat, as shown in FIG. 1, for example, the magnetization of the firstpinned magnetic layer 12 is pinned in the Y direction in the Figure.Once the magnetization of the first pinned magnetic layer 12 is pinnedin the Y direction in the Figure, the magnetization of the second pinnedmagnetic layer 14 which faces the first pinned magnetic layer 12 withthe nonmagnetic intermediate layer 12 introduced therebetween is pinnedin a manner antiparallel to the magnetization of the first pinnedmagnetic layer 12.

Optimally, in the present invention the thickness t_(P1) of the firstpinned magnetic layer 12 and the thickness t_(P2) of the second pinnedmagnetic layer 14, and (the thickness t_(P1) of the first pinnedmagnetic layer)/(the thickness t_(P2) of the second pinned magneticlayer) preferably is in a range of 0.33 to 0.95, or in a range of 1.05to 4.

A large exchange coupling magnetic field can be obtained within theseranges. However, the exchange coupling magnetic field tends to decreaseeven in these ranges if the thickness of the first pinned magnetic layer12 and the thickness of the second pinned magnetic layer 14 increases,so the present invention places the thickness of the first pinnedmagnetic layer 12 and the thickness of the second pinned magnetic layer14 appropriately.

With the present invention, it is preferable that the film thicknesst_(P1) of the first pinned magnetic layer 12 and the film thicknesst_(P2) of the second pinned magnetic layer 14 be both in a range of 10to 70 ängström, and that an absolute value obtained by subtracting thefilm thickness t_(P2) of the second pinned magnetic layer 14 from thefilm thickness t_(P1) of the first pinned magnetic layer 12 is equal toor greater than 2 ängström.

Adjusting the film thickness ratio and film thicknesses so as to bewithin the above ranges can yield an exchange coupling magnetic field(Hex) of at least 500 (Oe) or greater. Here, the term “exchange couplingmagnetic field” describes the magnitude of an external magnetic field atthe time that ΔMR (rate of resistance change) is half of the maximumΔMR, and the exchange coupling magnetic field (Hex) is a total conceptincluding the exchange coupling magnetic field (exchange anisotropicmagnetic field) generated at the interface between the first pinnedmagnetic layer 12 and the antiferromagnetic layer 11, the exchangecoupling magnetic field (RKKY interaction) generated between the firstpinned magnetic layer 12 and second pinned magnetic layer 14.

Also, with the present invention, it is even more preferable that (thethickness t_(P1) of the first pinned magnetic layer)/(the thicknesst_(P2) of the second pinned magnetic layer) be in a range of 0.53 to0.95, or in a range of 1.05 to 1.8. Also, in the above ranges, it ispreferable that the film thickness t_(P1) of the first pinned magneticlayer 12 and the film thickness t_(P2) of the second pinned magneticlayer 14 both be in a range of 10 to 50 ängström, and that an absolutevalue obtained by subtracting the film thickness t_(P2) of the secondpinned magnetic layer 14 from the film thickness t_(P1) of the firstpinned magnetic layer 12 is equal to or greater than 2 ängström.Adjusting the film thickness ratio of the first pinned magnetic layer 12and the second pinned magnetic layer 14, and the film thickness t_(P1)of the first pinned magnetic layer 12 and the film thickness t_(P2) ofthe second pinned magnetic layer 14, so as to be within the aboveranges, can yield an exchange coupling magnetic field of at least 1,000(Oe) or greater.

By keeping the film thickness ratio and film thicknesses within theabove ranges, the exchange coupling magnetic field (Hex) can beincreased, and also, the ΔMR (rate of resistance change) can be raisedto a level around the same as known arrangements.

The greater the exchange coupling magnetic field is, the greater thestability of the magnetization state of the first pinned magnetic layer12 and the second pinned magnetic layer 14 in an antiparallel state is.Particularly, the present invention uses a PtMn alloy which exhibitshigh blocking temperature as an antiferromagnetic layer 11, andgenerates a large exchange coupling magnetic field (exchange anisotropicmagnetic field) at the interface between the first pinned magnetic layer12 and the antiferromagnetic layer 11. Thus, the magnetization state ofthe first pinned magnetic layer 12 and the second pinned magnetic layer14 can be maintained in a thermally stable manner, as well.

Now, if that first pinned magnetic layer 12 and second pinned magneticlayer 14 are formed of the same material, and the first pinned magneticlayer 12 and second pinned magnetic layer 14 are formed at the samethickness, experimentation has shown that the exchange coupling magneticfield (Hex) and the ΔMR drops drastically.

It is supposed that this is due to the fact that, in the event that theMs·T_(P1) (magnetic moment) of the first pinned magnetic layer 12 andthe Ms·T_(P2) (magnetic moment) of the second pinned magnetic layer 14are the same value, an antiparallel state does not exist between themagnetization of the first pinned magnetic layer 12 and themagnetization of the second pinned magnetic layer 14, the amount ofdirectional dispersion of the magnetization (the amount of magneticmoment directed in various directions) increases. Consequently, therelative angle with the magnetization of a later-described free magneticlayer 16 cannot be appropriately controlled.

In order to solve such problems, it is first necessary to make the firstpinned magnetic layer 12 and the second pinned magnetic layer 14 havediffering Ms·t values, i.e., it is necessary to change the thickness ofthe first pinned magnetic layer 12 and the second pinned magnetic layer14 if the first pinned magnetic layer 12 and the second pinned magneticlayer 14 are to be formed of the same material.

As described above, the film thickness ratio between the first pinnedmagnetic layer 12 and the second pinned magnetic layer 14 is appropriateaccording to the present invention, so the range wherein the filmthickness t_(P1) of the first pinned magnetic layer 12 and the filmthickness t_(P2) of the second pinned magnetic layer 14 is approximatelythe same, specifically, the film thickness ratio range from 0.95 to1.05, is excluded from the appropriate range.

Next, if an antiferromagnetic material such as a PtMn alloy is used forthe antiferromagnetic layer 11 and is subjected to annealing (thermaltreatment) in a magnetic field following formation, as with the presentinvention, so as to generate a large exchange coupling magnetic field(exchange anisotropic magnetic field) at the interface between the firstpinned magnetic layer 12 and the antiferromagnetic layer 11, even in theevent that the first pinned magnetic layer 12 and the second pinnedmagnetic layer 14 are set to differing Ms·t values, the direction andmagnitude of the magnetic field applied during the thermal treatmentmust be appropriately controlled, or the amount of directionaldispersion of the magnetization of the first pinned magnetic layer 12and the magnetization of second pinned magnetic layer 14 may increase,or the magnetization may not be able to be controlled in a desireddirection.

TABLE 1 First pinned magnetic layer Ms · t_(P1) > second pinned magneticlayer Ms t_(P2) Magnetic (1) (2) (3) (4) direction 100 to 1 100 to 1 5kOe or 5 kOe or during thermal kOe to the kOe to the greater greatertreatment left right to the right to the left Direction of ← → → ← firstpinned magnetic layer Direction of → ← → ← second pinned magnetic layer

Table 1 shows how, in the event that Ms·t_(P1) of the first pinnedmagnetic layer 12 is greater than Ms·t_(P2) of the second pinnedmagnetic layer 14, changing the magnitude and direction of the magneticfield during thermal treatment changes the direction of magnetization ofthe first pinned magnetic layer 12 and second pinned magnetic layer 14.

In (1) shown in Table 1, 100 (Oe) to 1 k(Oe) is applied toward the leftin the Figure, as the direction of the magnetic field during thermaltreatment. In this case, Ms·t_(P1) of the first pinned magnetic layer 12is greater than Ms·t_(P2) of the second pinned magnetic layer 14, so themagnetization of the dominant first pinned magnetic layer 12 follows thedirection of the applied magnetic field and turns toward the left in theFigure, and the magnetization of the second pinned magnetic layer 14attempts to achieve an antiparallel state by the exchange couplingmagnetic field (RKKY interaction) generated with the first pinnedmagnetic layer 12.

In (2) shown in Table 1, a magnetic field of 100 (Oe) to 1 k(Oe) isapplied toward the right, so the magnetization of the dominant firstpinned magnetic layer 12 follows the direction of the applied magneticfield and turns toward the right in the Figure, and the magnetization ofthe second pinned magnetic layer 14 achieves an antiparallel state withthe magnetization of the first pinned magnetic layer 12.

In (3) shown in Table 1, a magnetic field of 5 k(Oe) or greater isapplied toward the right, so the magnetization of the dominant firstpinned magnetic layer 12 follows the direction of the applied magneticfield and turns toward the right. Now, the exchange coupling magneticfield (RKKY interaction) generated between the first pinned magneticlayer 12 and the second pinned magnetic layer 14 is about 1,000 (Oe) to5 k(Oe), so in the event that a magnetic field of 5 k(Oe) or greater isapplied, the second pinned magnetic layer 14 also follows the directionof the applied magnetic field, i.e., turns toward the right in theFigure. In the same way, in (4) shown in Table 1, a magnetic field of 5k(Oe) or greater is applied toward the left, so the magnetization of thefirst pinned magnetic layer 12 and the second pinned magnetic layer 14turn toward the left in the Figure.

TABLE 2 First pinned magnetic layer Ms t_(P1), < second pinned magneticlayer Ms · t_(P2) Magnetic (1) (2) (3) (4) direction 100 to 1 100 to 1 5kOe or 5 kOe or during thermal kOe to the kOe to the greater greatertreatment left right to the right to the left Direction of → ← → ← firstpinned magnetic layer Direction of ← → → ← second pinned magnetic layer

Table 2 shows how, in the event that Ms·t_(P1) of the first pinnedmagnetic layer 12 is smaller than Ms·t_(P2) of the second pinnedmagnetic layer 14, changing the magnitude and direction of the magneticfield during thermal treatment changes the direction of magnetization ofthe first pinned magnetic layer 12 and second pinned magnetic layer 14.

In (1) shown in Table 2, a magnetic field of 100 (Oe) to 1 k(Oe) isapplied toward the left in the Figure. In this case, the magnetizationof the second pinned magnetic layer 14 with the greater Ms·t_(P2)becomes dominant, so the magnetization of the second pinned magneticlayer 14 follows the direction of the applied magnetic field and turnstoward the left in the Figure. The magnetization of the first pinnedmagnetic layer 12 achieves an antiparallel state with the magnetizationof the second pinned magnetic layer 14 by the exchange coupling magneticfield (RKKY interaction) generated between the first pinned magneticlayer 12 and the second pinned magnetic layer 14. In the same way, in(2) shown in Table 2, a magnetic field of 100 (Oe) to 1 k(Oe) is appliedtoward the right, so the ma generation of the dominant second pinnedmagnetic layer 14 turns toward the right in the Figure, and themagnetization of the first pinned magnetic layer 12 turns to the left.

In (3) shown in Table 2, a magnetic field of 5 k(Oe) or greater isapplied toward the right in the Figure, so the magnetization of both thefirst pinned magnetic layer 12 and second pinned magnetic layer 14 turntoward the right in the Figure, due to the application of a magneticfield greater than the exchange coupling magnetic field (RKKYinteraction) generated between the first pinned magnetic layer 12 andthe second pinned magnetic layer 14. In (4) shown in Table 2, a magneticfield of 5 k(Oe) or greater is applied toward the left in the Figure, sothe magnetization of both the first pinned magnetic layer 12 and thesecond pinned magnetic layer 14 turn toward the left in the Figure.

Now, if that magnetization of the first pinned magnetic layer 12 is tobe directed toward the right direction in the Figure, for example, theappropriate direction and magnitude of the magnetic field for thermaltreatment is (2) and (3) in Table 1, and (1) and (3) in Table 2.

With (2) and (3) in Table 1, the magnetization of the first pinnedmagnetic layer 12 which has a greater Ms·t_(P1) is affected by theapplied magnetic field in the right direction during thermal treatment,and turns to the right. At this time, the magnetization of the firstpinned magnetic layer 12 is pinned in the right direction by theexchange coupling magnetic field (exchange anisotropic magnetic field)generated at the interface between the first pinned magnetic layer 12and the antiferromagnetic layer 11 by thermal treatment. In (3) in Table1, removing the magnetic field of 5 k(Oe) or greater causes themagnetization of the second pinned magnetic layer 14 to invert due tothe exchange coupling magnetic field (RKKY interaction) generatedbetween the first pinned magnetic layer 12 and the second pinnedmagnetic layer 14, and turn to the left.

In the same way, with (1) and (3) in Table 2, the magnetization of thefirst pinned magnetic layer 12 facing in the right direction is pinnedin the right direction by the exchange coupling magnetic field (exchangeanisotropic magnetic field) at the interface between the first pinnedmagnetic layer 12 and the antiferromagnetic layer 11. In (3) in Table 2,removing the magnetic field of 5 k(Oe) or greater causes themagnetization of the second pinned magnetic layer 14 to invert due tothe exchange coupling magnetic field (RKKY interaction) generatedbetween the first pinned magnetic layer 12 and the second pinnedmagnetic layer 14, and be pinned towards the left.

Now, as can be seen from Table 1 and Table 2, the magnitude of themagnetic field applied during thermal treatment is either 100 (Oe) to 1k(Oe), or 5 k(Oe) or greater, with magnetic fields in the range of 1,000(Oe) to 5 k(Oe) being excluded from the appropriate range. The reason isas follows.

When a magnetic field is applied, the magnetization of the pinnedmagnetic layer with a greater Ms t attempts to turn in the direction ofthat magnetic field. However, if the magnitude of the magnetic field isin the range of 1,000 (Oe) to 5 k(Oe) during thermal treatment, themagnetization of the pinned magnetic layer with a smaller Ms·t also isstrongly affected by the magnetic field and attempts to turn in thedirection of that magnetic field.

Accordingly, the magnetization of each of the two pinned magnetic layerswhich should attempt to achieve an antiparallel state due to theexchange coupling magnetic field (RKKY interaction) generated betweenthe pinned magnetic layers are affected by the strong magnetic field anddo not become antiparallel, the amount of so-called directionaldispersion of the magnetization wherein the magnetic moment is directedin various directions increases and consequently the magnetization ofeach of the two pinned magnetic layers cannot be appropriatelymagnetized in an antiparallel state. Accordingly, magnetic fields in therange of 1,000 (Oe) to 5 k(Oe) are excluded from the appropriate rangein the present invention. The reason that the magnitude of the magneticfield during thermal treatment is set at 100 (Oe) or greater is that amagnetic field any weaker is not capable of directing the magnetizationof the pinned magnetic layer with a great Ms t in the direction of thatmagnetic field.

The above-described method of controlling the magnitude and direction ofthe magnetic field during thermal treatment can be used for any sort ofantiferromagnetic material as long as this is for an antiferromagneticlayer 11 which requires thermal treatment, and is also applicable tocases using an NiMn alloy, which is conventionally used for theantiferromagnetic layer 11.

In this way, the pre sent invention is capable of increasing theexchange coupling magnetic field (Hex) by keeping the film thicknessratio of the first pinned magnetic layer 12 and the second pinnedmagnetic layer 14 within an appropriate range. The present invention isalso capable of maintaining the magnetization of the first pinnedmagnetic layer 12 and the second pinned magnetic layer 14 in a thermallystable antiparallel state (Ferri-state), and further enables ΔMR (rateof resistance change) to be maintained at a level around the same asthat of known arrangements.

Further, appropriately controlling the magnitude and direction of themagnetic field during thermal treatment enables the magnetizationdirection of the first pinned magnetic layer 12 and the second pinnedmagnetic layer 14 to be controlled in a de sired direction.

Now, the magnetic moment (magnetic film thickness) such as describedearlier can be calculated as the product of the saturation magnetizationMs and film thickness t. For example, it is known that with bulk solidNiFe, the saturation magnetization Ms is approximately 1.0 T (tesla),and that with bulk solid Co, the saturation magnetization Ms isapproximately 1.7 T. Accordingly, if the film thickness of theaforementioned NiFe is 30 ängström, the magnetic film thickness of theNiFe film is 30 ängström tesla. The magnetostatic energy of aferromagnetic film when a magnetic field is externally applied isproportionate to the magnetic film thickness and external magnetic fieldmultiplied, so if a ferromagnetic film with a great magnetic filmthickness and a ferromagnetic film with a small magnetic film thicknessare in a Ferri-state by RKKY interaction with a nonmagnetic intermediatelayer introduced therebetween, the ferromagnetic film with the greatermagnetic film thickness tends to be directed in the direction of theexternal magnetic field.

However, it is known that if the ferromagnetic film is in layeredcontact with nonmagnetic film such as tantalum (Ta), ruthenium (Ru),copper (CU), etc., or if the ferromagnetic film is in layered contactwith an antiferromagnetic layer (such as a PtMn film or the like), thesaturation magnetization Ms of the ferromagnetic film near the interfacewith the nonmagnetic film or antiferromagnetic film becomes smaller thanthe saturation magnetization Ms of the bulk solid, since the nonmagneticfilm atoms or antiferromagnetic film atoms are in direct contact withthe ferromagnetic film atoms (Ni, Fe, Co). Further, it is known that ifthermal treatment is performed on multi-layered film of ferromagneticfilm and nonmagnetic film, antiferromagnetic layers, interfacedispersion advances due to the thermal treatment, and distribution inthe thickness direction of the film appears in the saturationmagnetization Ms of the ferromagnetic film. That is to say, this is thephenomena wherein the saturation magnetization Ms is small at areas nearnonmagnetic film or antiferromagnetic layers, but the saturationmagnetization Ms nears the saturation magnetization Ms of the bulk solidas the position draws away from the interface with the nonmagnetic filmor antiferromagnetic film.

Reduction in the saturation magnetization Ms of the ferromagnetic filmat areas near nonmagnetic film or antiferromagnetic film depends on thematerial for the nonmagnetic film, the material for theantiferromagnetic film, order of layering, thermal treating temperature,etc., and each must be accurately obtained under certain conditions. Themagnetic film thickness according to the present invention is a valuewhich has been calculated, taking into consideration the amount ofreduction of the saturation magnetization Ms generated by thermaldispersion with the nonmagnetic film or antiferromagnetic layers.

In order to obtain an exchange coupling magnetic field at the interfacebetween the PtMn film and ferromagnetic film due to thermal treatment, adispersion layer must be formed at the interface between the PtMn filmand ferromagnetic film, but the reduction of the saturationmagnetization Ms of the ferromagnetic film at the time of forming thedispersion layer depends on the order of layering the PtMn film andferromagnetic film.

Particularly, as shown in FIG. 1, if the antiferromagnetic layer 11 issituated lower than the free magnetic layer 16, a thermal dispersionlayer easily occurs at the interface of the antiferromagnetic layer 11and the first pinned magnetic layer 12. Accordingly, the magnetic filmthickness of the first pinned magnetic layer 12 is smaller than theactual film thickness t_(P1). However, if the magnetic film thickness ofthe first pinned magnetic layer 12 becomes too small, the difference inmagnetic film thickness (magnetic moment) with the second pinnedmagnetic layer 14 becomes too great, and the ratio of thermal dispersionlayer in the first pinned magnetic layer 12 becomes too great, leadingto a problematic deterioration of the exchange coupling magnetic field.

That is, as with the case of the present invention, in order to use anantiferromagnetic layer 11 which requires thermal treatment to generatean exchange coupling magnetic field at the interface with the firstpinned magnetic layer 12, to create a Ferri-state in the magnetizationstate between the first pinned magnetic layer 12 and second pinnedmagnetic layer 14, the magnetic film thickness of the first pinnedmagnetic layer 12 and second pinned magnetic layer 14 must be optimized,in addition to optimizing the film thickness of the first pinnedmagnetic layer 12 and second pinned magnetic layer 14. Otherwise, astable magnetization state cannot be obtained.

As described above, unless there is a certain degree of difference inmagnetic film thickness between the first pinned magnetic layer 12 andsecond pinned magnetic layer 14, the magnetization state does not easilyachieve a Ferri-state. On the other hand, if the difference in magneticfilm thickness between the first pinned magnetic layer 12 and secondpinned magnetic layer 14 is too large, undesirable deterioration in theexchange coupling magnetic field results. Accordingly, with the presentinvention, as with the film thickness of the first pinned magnetic layer12 and second pinned magnetic layer 14, it is preferable that (themagnetic film thickness of the first pinned magnetic layer 12)/(themagnetic film thickness of the second pinned magnetic layer 14) be in arange of 0.33 to 0.95, or in a range of 1.05 to 4. Also, with thepresent invention, it is preferable that the magnetic film thickness ofthe first pinned magnetic layer 12 and the magnetic film thickness ofthe second pinned magnetic layer 14 be in a range of 10 to 70 (ängströmtesla), and that an absolute value obtained by subtracting the magneticfilm thickness of the second pinned magnetic layer 14 from the magneticfilm thickness of the first pinned magnetic layer 12 is equal to orgreater than 2 (ängström tesla).

It is even more preferable that (the magnetic film thickness of thefirst pinned magnetic layer 12)/(the magnetic film thickness of thesecond pinned magnetic layer 14) be in a range of 0.53 to 0.95 or in arange of 1.05 to 1.8. Also, in the above ranges, it is preferable thatthe magnetic film thickness of the first pinned magnetic layer 12 andthe magnetic film thickness of the second pinned magnetic layer 14 be ina range of 10 to 50 (ängström tesla), and that an absolute valueobtained by subtracting the film thickness of the second pinned magneticlayer 14 from the film thickness of the first pinned magnetic layer 12is equal to or greater than 2 (ängström tesla).

Next, the nonmagnetic intermediate layer 13 introduced between the firstpinned magnetic layer 12 and the second pinned magnetic layer 14 in FIG.1 will be described.

With the present invention, the nonmagnetic intermediate layer 13introduced between the first pinned magnetic layer 12 and the secondpinned magnetic layer 14 is preferably formed of one of the following;or of an alloy of two or more thereof: Ru, Rh, Ir, Cr, Re, and Cu.

In the present invention, the appropriate film thickness value of thenonmagnetic intermediate layer 13 is changed according to whether theantiferromagnetic layer 11 is formed below or above a later-describedfree magnetic layer 16.

As shown in FIG. 1, the film thickness value of the nonmagneticintermediate layer 13 if the antiferromagnetic layer 11 is formed belowthe free magnetic layer 16 is preferably in the range of 3.6 to 9.6ängström. Within this range, an exchange coupling magnetic field (Hex)of 500 (Oe) or greater can be obtained.

It is further preferable that the film thickness value of thenonmagnetic intermediate layer 13 be in the range of 4 to 9.4 ängström,since an exchange coupling magnetic field of 1,000 (Oe) or greater canbe obtained.

Experimentation has shown that the exchange coupling magnetic fielddrastically drops the nonmagnetic intermediate layer 13 is formed to athickness other than the above-described dimensions. That is to say, inthe event that the nonmagnetic intermediate layer 13 is formed to athickness other than that described above, the magnetization of thefirst pinned magnetic layer 12 and the second pinned magnetic layer 14does not easily achieve an antiparallel state (Ferri-state), so there isthe problem of instability in the magnetization state.

As shown in FIG. 1, a nonmagnetic electrically conductive layer 15 of Cuor the like is formed on the second pinned magnetic layer 14, andfurther, a free magnetic layer 16 is formed on the nonmagneticelectrically conductive layer 15. As shown in FIG. 1, the free magneticlayer 16 is comprised of two layers, and the layer denoted by thereference numeral 17 that is formed to the side which comes into contactwith the nonmagnetic electrically conductive layer 15 is comprised of aCo film. The other layer 18 is comprised of an NiFe alloy, Co—Fe alloy,Co—Ni alloy, Co—NiFe alloy, or the like. The reason that the Co filmlayer 17 is formed to the side which comes into contact with thenonmagnetic electrically conductive layer 15, is that dispersion ofmetal elements and the like at the interface between the Co film layer17 and the nonmagnetic electrically conductive layer 15 formed of Cu canbe prevented, and the ΔMR (rate of resistance change) can be raised.Reference numeral 19 denotes a protective layer formed of Ta or thelike. As shown in FIG. 2, hard magnetic bias layers 130 formed of aCo—Pt alloy, Co—Cr—Pt alloy, or the like, and electrically conductivelayers 131 formed of Cu and Cr, are formed on either side of the layeredstructure from the base layer 10 to the protective layer 19, and themagnetization of the free magnetic layer 16 is affected by the biasmagnetic field of the hard magnetic bias layer and is thus magnetized inthe direction X in the Figure.

With the spin-valve magnetoresistive thin film element shown in FIG. 1,sensing current is provided from the above electrically conductive layerto the free magnetic layer 16, nonmagnetic electrically conductive layer15, and second pinned magnetic layer 14. In the event that a magneticfield is provided from the recording medium in the direction Y shown inFIG. 1, the magnetization of the free magnetic layer 16 changes from thedirection X in the Figure to the direction Y in the Figure, andscattering of conduction electrons dependent on spinning occurs at theinterface between the nonmagnetic electrically conductive layer 15 andfree magnetic layer 16, and at the interface between the nonmagneticelectrically conductive layer 15 and the second pinned magnetic layer14, whereby electric resistance changes, and consequently the leakagemagnetic field of the recording medium is detected.

Now, this sensing current also flows to the interface between the firstpinned magnetic layer 12 and nonmagnetic intermediate layer 13, and soforth. The first pinned magnetic layer 12 does not directly contributeto ΔMR, so the first pinned magnetic layer 12 has a supplementary roleof pinning the second pinned magnetic layer 14, which contributes toΔMR, in an appropriate direction. Accordingly, the sensing currentflowing to the first pinned magnetic layer 12 and nonmagneticintermediate layer 13 results in shunt loss (current loss), but theamount of this shunt loss is very small, and the present invention canobtain ΔMR of around the same as known arrangements.

Now, experimentation has shown that, with the present invention,dividing the first pinned magnetic layer 12 and second pinned magneticlayer 14 with the nonmagnetic intermediate layer 13 introducedtherebetween a large exchange coupling magnetic field (Hex) can beobtained even in the event that the thickness of the antiferromagneticlayer 11 is reduced, specifically, 500 (Oe) or greater can be obtained.

With known arrangements, in the event that a PtMn alloy is used in asingle spin-valve magnetoresistive thin film element as theantiferromagnetic layer 11, a thickness of at least 200 ängström orgreater has to be secured in order to obtain an exchange couplingmagnetic field of 500 (Oe) or greater. However, with the presentinvention, a thickness of at least 90 ängström or greater for theantiferromagnetic layer 11 can obtain an exchange coupling magneticfield of 500 (Oe) or greater. Further, a thickness of at least 100ängström or greater can obtain an exchange coupling magnetic field of1,000 (Oe) or greater. Now, these values for the antiferromagnetic layer11 are for a single spin-valve magnetoresistive thin film element, andthe appropriate film thickness ranges differ somewhat for so-called dualspin-valve magnetoresistive thin film elements wherein antiferromagneticlayers are formed above and below the free magnetic layer. Dualspin-valve magnetoresistive thin film elements will be described later.

Thus, according to the present invention, the antiferromagnetic layer 11which is the largest layer in a spin-valve magnetoresistive thin filmelement can be formed at half or less of the thickness required in knownarrangements, thereby enabling reduction of the overall thickness of thespin-valve magnetoresistive thin film element.

FIG. 13 is a cross-sectional view of a the structure of a reading headon which a spin-valve magnetoresistive thin film element is formed,viewed from the side facing the recording medium.

Reference numeral 120 denotes a lower shield layer formed of an NiFealloy, for example, and a lower gap layer 121 is formed on the lowershield layer 120. Also, a spin-valve magnetoresistive thin film element122 according to the present invention is formed on the lower gap layer121, and hard magnetic bias layers 123 and electrically conductivelayers 124 are formed on either side of the spin-valve magnetoresistivethin film element 122. An upper gap layer 125 is formed on theelectrically conductive layers 124, and an upper shield layer 126 formedof an NiFe alloy or the like is formed on the upper gap layer 125.

The lower gap layer 121 and upper gap layer 125 are formed of aninsulating material such as SiO₂ or Al₂O₃ (alumina). As shown in FIG.13, the length from the lower gap layer 121 to the upper gap layer 125is represented by G1, and the smaller this G1 is the higher therecording density that can be handled is.

As described above, the present invention enables reduction of theoverall thickness of the spin-valve magnetoresistive thin film element122 by reducing the thickness of the antiferromagnetic layer 11, so thegap length G1 can be reduced. Further, even in the event that the lowergap layer 121 and the upper gap layer 125 are made to be relativelythick, the gap length G1 can be made relatively small; forming the lowergap-layer 121 and the upper gap layer 125 relatively thick securessufficient insulation.

The spin-valve magnetoresistive thin film element shown in FIG. 1 isformed by layering the following layers in order from the bottom up: thebase layer 10, antiferromagnetic layer 11, first pinned magnetic layer12, nonmagnetic intermediate layer 13, second pinned magnetic layer 14,nonmagnetic electrically conductive layer 15, free magnetic layer 16,and protective layer 19, following which a process of annealing (thermaltreatment) is performed in a magnetic field.

With the spin-valve magnetoresistive thin film element shown in FIG. 1,the thickness t_(P1), of the first pinned magnetic layer 12 is formed soas to be thinner than the thickness t_(P2) of the second pinned magneticlayer 14, and the magnetic moment (Ms t_(P1)) of the first pinnedmagnetic layer 12 is set so as to be smaller than the magnetic moment(Ms·t_(P2)) of the second pinned magnetic layer 14.

In this case, a magnetic field of 100 to 1000 (Oe) is applied in thedirection opposite to the direction in which the magnetization of thesecond pinned magnetic layer 14 is to be directed, or a magnetic fieldof 5 k(Oe) or greater is applied in the direction in which themagnetization of the second pinned magnetic layer 14 is to be directed.

As shown in FIG. 1, if that the magnetization of the first pinnedmagnetic layer 12 is to be pinned in the direction Y shown in theFigure, referring to the above Table 2 will show that either a magneticfield of 100 (Oe) to 1 k(Oe) (See Table 2 (1)) should be applied in thedirection opposite to the direction Y in the Figure, or a magnetic fieldof 5 k(Oe) or greater should be applied in the direction Y (See Table 2(3)).

Applying a magnetic field of 100 (Oe) to 1 k(Oe) in the directionopposite to the direction Y magnetizes the second pinned magnetic layer14 which has greater magnetic moment (Ms t_(P2)) in the directionopposite to the direction Y, the magnetization of the first pinnedmagnetic layer 12 which is magnetized in an antiparallel manner due tothe exchange coupling magnetic field (RKKY interaction) generatedbetween the first pinned magnetic layer 12 and the second pinnedmagnetic layer 14 is directed in the direction Y in the FIG. 1, and themagnetization of the first pinned magnetic layer 12 is pinned in thedirection Y in the Figure due to the exchange coupling magnetic field(exchange anisotropic magnetic field) generated at the interface betweenthe first pinned magnetic layer 12 and the antiferromagnetic layer 11.

As a result of the magnetization of the first pinned magnetic layer 12being pinned in the direction Y in the Figure, magnetization of thesecond pinned magnetic layer 14 is pinned in an antiparallel manner withthe magnetization of the first pinned magnetic layer 12.

Alternatively, applying a magnetic field of 5 k(Oe) or greater. in thedirection Y magnetizes both the first pinned magnetic layer 12 andsecond pinned magnetic layer 14 in the direction Y in the Figure, andthe magnetization of the first pinned magnetic layer 12 is pinned in thedirection Y in the Figure due to the exchange coupling magnetic field(exchange anisotropic magnetic field) generated at the interface betweenthe first pinned magnetic layer 12 and the antiferromagnetic layer 11.Removing the magnetic field of 5 k(Oe) or greater causes themagnetization of the second pinned magnetic layer 14 to be inverted dueto the exchange coupling magnetic field (RKKY interaction) generatedbetween the first pinned magnetic layer 12 and the second pinnedmagnetic layer 14, and thus be pinned in the direction opposite to thedirection Y in the Figure.

If the magnetic moment of the first pinned magnetic layer 12 is greaterthan the magnetic moment of the second pinned magnetic layer 14, amagnetic field of 100 (Oe) to 1,000 (Oe) or a magnetic field of 5 k(Oe)or greater is applied in the direction which the magnetization of thefirst pinned magnetic layer 12 is to be directed.

Now, the spin-valve magnetoresistive thin film element shown in FIG. 1is the most important part comprising the reproducing head(magnetoresistive thin film head). First, a gap layer is formed on thelower shield layer of magnetic material, following which the spin-valvemagnetoresistive thin film element is formed. Subsequently, forming anupper shield layer on the spin-valve magnetoresistive thin film elementwith a gap layer introduced therebetween completes the reproducing head(MR head). Further, a recording inductive head having a core formed ofmagnetic material and a coil, may be provided thereupon. In this case,the above upper shield layer is preferably used to serve as the lowercore layer of the inductive head. Shield layers are formed above andbelow the spin-valve magnetoresistive thin film elements shown in FIG. 3and the subsequent drawings, as with the spin-valve magnetoresistivethin film element shown in FIG. 1.

FIG. 3 is a side cross-sectional view schematically showing thestructure of a spin-valve magnetoresistive thin film element accordingto a second embodiment of the present invention, and FIG. 4 is across-sectional view of the spin valve magnetoresistive thin filmelement shown in FIG. 3, viewed from the side facing the recordingmedium.

This spin-valve magnetoresistive thin film element is a singlespin-valve magnetoresistive thin film element which has been formed byreversing the order of layers of the spin-valve magnetoresistive thinfilm element shown in FIG. 1.

That is, the spin-valve magnetoresistive thin film element shown in FIG.3 comprises from the bottom: A base layer 10, NiFe film 22, Co film 23(the NiFe film 22 and Co film 23 together comprising a free magneticlayer 21), nonmagnetic electrically conductive layer 24, second pinnedmagnetic layer 25, nonmagnetic intermediate layer 26, first pinnedmagnetic layer 27, antiferromagnetic layer 28, and protective layer 29,in that order.

It is preferable that the antiferromagnetic layer 28 be formed of a PtMnalloy, but X—Mn alloys (wherein X is one or a plurality of the followingelements: Pd, Ir, Rh, Ru, Os) or PtMn—X alloys (wherein X, is one or aplurality of the following elements: Pd, Ir, Rh, Ru, Os, Au, Ag) may beused instead of PtMn alloys.

With this spin-valve magnetoresistive thin film element as well, it ispreferable that the film thickness ratio between the film thicknesst_(P1) of the first pinned magnetic layer 27 and the film thicknesst_(P2) of the second pinned magnetic layer 25 be such wherein (filmthickness t_(P1) of first pinned magnetic layer)/(film thickness t_(P2)of second pinned magnetic layer) is in a range of 0.33 to 0.95, or in arange of 1.05 to 4, and even more preferably, in a range of 0.53 to 0.95or 1.05 to 1.8. Also, it is preferable that the film thickness t_(P1),of the first pinned magnetic layer 27 and the film thickness t_(P2) ofthe second pinned magnetic layer 25 be in a range of 10 to 70 ängström,and that an absolute value obtained by subtracting the film thicknesst_(P2) of the second pinned magnetic layer 25 from the film thicknesst_(P1) of the first pinned magnetic layer 27 is equal to or greater than2 ängström. Even more preferable is an arrangement wherein the filmthickness t_(P1) of the first pinned magnetic layer 27 and the filmthickness t_(P2) of the second pinned magnetic layer 25 is in a range of10 to 50 ängström, and that the absolute value obtained by subtractingthe film thickness t_(P2) of the second pinned magnetic layer 25 fromthe film thickness t_(P1) of the first pinned magnetic layer 27 is equalto or greater than 2 ängström.

As described above, unless there is a certain degree of difference inmagnetic film thickness between the first pinned magnetic layer 27 andsecond pinned magnetic layer 25, the magnetization state does not easilyachieve a Ferri-state; on the other hand, if that the difference inmagnetic film thickness between the first pinned magnetic layer 27 andsecond pinned magnetic layer 25 is too great, this leads to undesirabledeterioration in the exchange coupling magnetic field. Accordingly, withthe present invention, as with the film thickness ratio of the firstpinned magnetic layer 27 and second pinned magnetic layer 25, it ispreferable that (the magnetic film thickness Ms t_(P1), of the firstpinned magnetic layer 27)/(the magnetic film thickness Ms t_(P2) of thesecond pinned magnetic layer 25) be in a range of 0.33 to 0.95, or in arange of 1.05 to 4.

Also, with the present invention, it is preferable that the magneticfilm thickness Ms t_(P1) of the first pinned magnetic layer 27 and themagnetic film thickness Ms·t_(P2) of the second pinned magnetic layer 25be in a range of 10 to 70 (ängström tesla), and that an absolute valueobtained by subtracting the magnetic film thickness Ms·t_(P2) of thesecond pinned magnetic layer 25 from the magnetic film thicknessMs·t_(P1) of the first pinned magnetic layer 27 is equal to or greaterthan 2 (ängström tesla).

It is even more preferable that (the magnetic film thickness Ms·t_(P1)of the first pinned magnetic layer 27)/(the magnetic film thicknessMs·t_(P2) of the second pinned magnetic layer 25) be in a range of 0.53to 0.95 or in a range of 1.05 to 1.8. Also, in the above ranges, it ispreferable that the magnetic film thickness Ms·t_(P1) of the firstpinned magnetic layer 27 and the magnetic film thickness Ms·t_(P2) ofthe second pinned magnetic layer 25 be in a range of 10 to 50 (ängströmtesla), and that an absolute value obtained by subtracting the magneticfilm thickness Ms·t_(P2) of the second pinned magnetic layer 25 from themagnetic film thickness Ms·t_(P1) of the first pinned magnetic layer 27be equal to or greater than 2 (ängström tesla).

The nonmagnetic intermediate layer 26 introduced between the firstpinned magnetic layer 27 and the second pinned magnetic layer 25 shownin FIG. 3 is preferably formed of one of the following; or of an alloyof two or more thereof: Ru, Rh, Ir, Cr, Re, and Cu.

With the present invention, as shown in FIG. 3, the film thickness valueof the nonmagnetic intermediate layer 26 if that the antiferromagneticlayer 28 is formed above the free magnetic layer 21 is preferably in therange of 2.5 to 6.4 ängström, or 6.6 to 10.7 ängström. Within thisrange, an exchange coupling magnetic field (Hex) of 500 (Oe) or greatercan be obtained.

It is further preferable that the film thickness value of the,nonmagnetic intermediate layer 26 be in the range of 2.8 to 6.2ängström, or 6.8 to 10.3 ängström. Within this range, an exchangecoupling magnetic field (Hex) of at least 1,000 (Oe) or greater can beobtained.

Also, a thickness of at least 90 ängström or greater for theantiferromagnetic layer 28 can obtain an exchange coupling magneticfield of 500 (Oe) or greater. Further, a thickness of at least 100ängström or greater can obtain an exchange coupling magnetic field of1,000 (Oe) or greater.

With the spin-valve magnetoresistive thin film element shown in FIG. 3,the film thickness t_(P1) of the first pinned magnetic layer 27 isformed so as to have a different value to the film thickness t_(P2) ofthe second pinned magnetic layer 25, with the film thickness t_(P1) ofthe first pinned magnetic layer 27 being thicker the film thicknesst_(P2) of the second pinned magnetic layer 25, for example. Also, themagnetization of the first pinned magnetic layer 27 is magnetized in thedirection Y in the Figure, while the magnetization of the second pinnedmagnetic layer 25 is magnetized in the opposite direction to Y in theFigure, so the magnetization of the first pinned magnetic layer 27 andof the second pinned magnetic layer 25 are in a Ferri-state. The methodfor controlling the magnetization direction for the first pinnedmagnetic layer 27 and second pinned magnetic layer 25 shown in FIG. 3will now be described.

First, each of the layers shown in FIG. 3 are formed by sputtering orthe like, and subjected to annealing (thermal treatment) in a magneticfield in the process following forming of the films.

In the event that the Ms·t_(P1) (magnetic moment) of the first pinnedmagnetic layer 27 is greater than the Ms·t_(P2) (magnetic moment) of thesecond pinned magnetic layer 25, a magnetic field of 100 (Oe) to 1 k(Oe)or 5 k(Oe) should be applied in the direction which the magnetization ofthe first pinned magnetic layer 27 is to be directed.

As shown in FIG. 3, if the first pinned magnetic layer 27 with a greaterMs·t_(P1) is to be directed in the direction Y in the Figure, referringto the above Table 1 shows that a magnetic field of 100 (Oe) to 1 k(Oe)(see Table 1 (2)) or 5 k(Oe) (see Table 1 (3))should be applied in thedirection Y.

Applying the magnetic field of 100 (Oe) to 1 k(Oe) in the direction Y inthe Figure causes the magnetization of the first pinned magnetic layer27 with the greater Ms·t_(P1) to be directed in the direction Y, and themagnetization of the second pinned magnetic layer 25 attempts to achievean antiparallel state. Then, the magnetization of the first pinnedmagnetic layer 27 is pinned in the direction Y in the Figure due to theexchange coupling magnetic field (exchange anisotropic magnetic field)generated at the interface between the first pinned magnetic layer 27and the antiferromagnetic layer 28, and consequently, the magnetizationof the second pinned magnetic layer 25 is pinned in a direction oppositeto the direction Y.

Or, applying a magnetic field of 5 k(Oe) or greater in the direction Yin the Figure magnetizes the magnetization of both the first pinnedmagnetic layer 27 and second pinned magnetic layer 25 in the direction Yin the Figure, due to a magnetic field greater than the exchangecoupling magnetic field (RKKY interaction) generated between the firstpinned magnetic layer 27 and the second pinned magnetic layer 25 beingapplied. The magnetization of the first pinned magnetic layer 27 ispinned in the direction Y in the Figure due to the exchange couplingmagnetic field (exchange anisotropic magnetic field) generated at theinterface between the first pinned magnetic layer 27 and theantiferromagnetic layer 28. On the other hand, removing the appliedmagnetic field causes the magnetization of the second pinned magneticlayer 25 to be inverted due to the. exchange coupling magnetic field(RKKY interaction) generated between the first pinned magnetic layer 27and the second pinned magnetic layer 25, and thus be pinned in a stateantiparallel with the magnetization of the first pinned magnetic layer27.

Alternatively, if the magnetic moment of the first pinned magnetic layer27 is smaller than the magnetic moment of the second pinned magneticlayer 25, a magnetic field of 100 (Oe) to 1,000 (Oe) is applied in thedirection opposite to the direction in which the magnetization of thefirst pinned magnetic layer 27 is to be directed, or a magnetic field of5 k(Oe) or greater is applied in the direction in which themagnetization is to be directed.

As shown in FIG. 4, hard magnetic bias layers 130 and electricallyconductive layers 131 are formed on either side of the layered structurefrom the base layer 10 to the protective layer 29, and the magnetizationof the free magnetic layer 21 is affected by the bias magnetic field ofthe hard magnetic bias layer 130 magnetized in the direction X in theFigure, and thereby aligned in the direction X.

FIG. 5 is a side cross-sectional view schematically showing thestructure of a spin-valve magnetoresistive thin film element accordingto a third embodiment of the present invention, and FIG. 6 is across-sectional view of the spin-valve magnetoresistive thin filmelement shown in FIG. 5, viewed from the side facing the recordingmedium.

This spin-valve magnetoresistive thin film element is a so-called dualspin-valve magnetoresistive thin film element comprising one each ofnonmagnetic electrically conductive layers, pinned magnetic layers, andantiferromagnetic layers formed above and below a free magnetic layer asthe center thereof. With this dual spin-valve magnetoresistive thin filmelement, there are two sets of the three layers of free magneticlayer/nonmagnetic electrically conductive layer/pinned magnetic layer,so a large ΔMR can be expected as compared to single spin-valvemagnetoresistive thin film elements, and thus is capable of dealing withhigh-density recording.

The spin-valve magnetoresistive thin film element shown in FIG. 5 isformed by layering the following layers in order from the bottom up: thebase layer 30, antiferromagnetic layer 31, first pinned magnetic layer(lower) 32, nonmagnetic intermediate layer (lower) 33, second pinnedmagnetic layer (lower) 34, nonmagnetic electrically conductive layer 35,free magnetic layer 36 (reference numerals 37 and 39 denoting Co films,and reference numeral 38 denoting an NiFe alloy film), nonmagneticelectrically conductive layer 40, second pinned magnetic layer (upper)41, nonmagnetic intermediate layer (upper) 42, first pinned magneticlayer (upper) 43, antiferromagnetic layer 44, and protective layer 45.As shown in FIG. 6, hard magnetic bias layers 130 and electricallyconductive layers 131 are formed on either side of the layered structurefrom the base layer 30 to the protective layer 45.

It is preferable that the antiferromagnetic layers 31 and 44 of thespin-valve magnetoresistive thin film element shown in FIG. 5 be formedof a PtMn alloy, but X—Mn alloys (wherein X is one or a plurality of thefollowing elements: Pd, Ir, Rh, Ru, Os) or PtMn—X alloys (wherein X′ isone or a plurality of the following elements: Pd, Ir, Rh, Ru, Os, Au,Ag) may be used instead of PtMn alloys.

With this spin-valve magnetoresistive thin film element as well, it ispreferable that the film thickness ratio between the film thicknesst_(P1) of the first pinned magnetic layer (lower) 32 and the filmthickness t_(P2) of the second pinned magnetic layer (lower) 34, and thefilm thickness ratio between the film thickness t_(P1) of the firstpinned magnetic layer (upper) 43 and the film thickness t_(P2) of thesecond pinned magnetic layer (upper) 41 be such wherein (film thicknesst_(P1) of first pinned magnetic layer)/(film thickness t_(P2) of secondpinned magnetic layer) is in a range of 0.33 to 0.95, or in a range of1.05 to 4. Also, if the film thickness ratio is in the above range, andthat the film thickness t_(P1) of the first pinned magnetic layer(lower) 32 and (upper) 43, and the film thickness t_(P2) of the secondpinned magnetic layer (lower) 34 and (upper) 41 is in a range of 10 to70 ängström, and that an absolute value obtained by subtracting the filmthickness t_(P2) of the second pinned magnetic layers 34 and 41 from thefilm thickness t_(P1) of the first pinned magnetic layers 32 and 43 isequal to or greater than 2 ängström, an exchange coupling magnetic fieldof 500 (Oe) or greater can be obtained.

Even more preferable with the present invention is an arrangementwherein the (film thickness t_(P1) of first pinned magnetic layer)/(filmthickness t_(P2) of second pinned magnetic layer) is in a range of 0.53to 0.95, or in a range of 1.05 to 1.8, and moreover, in the event thatthe film thickness t_(P1) of the first pinned magnetic layers (lower) 32and (upper) 43, and the film thickness t_(P2) of the second pinnedmagnetic layers (lower) 34 and (upper) 41, is in a range of 10 to 50ängström, and that the absolute value obtained by subtracting the filmthickness t_(P2) of the second pinned magnetic layers 34 and 41 from thefilm thickness t_(P1) of the first pinned magnetic layers 32, 43 isequal to or greater than 2 ängström, an exchange coupling magnetic fieldof 1,000 (Oe) or greater can be obtained.

Now, experimentation has shown that even if the thickness t_(P1) of thefirst pinned magnetic layer (lower) 32 formed below the free magneticlayer 36 is made to be greater than the thickness t_(P2) of the secondpinned magnetic layer (lower) 34, the exchange coupling magnetic fieldtends to drop if the difference in film thickness between the thicknesst_(P1) of the first pinned magnetic layer (lower) 32 and the thicknesst_(P2) of the second pinned magnetic layer (lower) 34 is equal to orlower than 6 ängström.

This phenomena is observed in the event that the antiferromagneticlayers 31 and 44 used are formed of a PtMn alloy or the like whichrequires thermal treatment in order to generate an exchange couplingmagnetic field (exchange anisotropic magnetic field) at the interfacebetween the first pinned magnetic layer (lower) 32 and (upper) 43.

This drop in the exchange coupling magnetic field occurs due to thefollowing: thermal dispersion between the antiferromagnetic layer 31formed below the free magnetic layer 36 and the first pinned magneticlayer (lower) 32 causes the magnetic film thickness of the first pinnedmagnetic layer (lower) 32 to decrease, to the extent that the magneticfilm thickness of the first pinned magnetic layer (lower) 32 and thefilm thickness t_(P2) of the second pinned magnetic layer 34 isapproximately the same. Accordingly, with the present invention, the(film thickness t_(P1) of the first pinned magnetic layer (lower)32/film thickness t_(P2) of the second pinned magnetic layer (lower) 34)is preferably made to be greater than the (film thickness t_(P1) of thefirst pinned magnetic layer (upper) 43/film thickness t_(P2) of thesecond pinned magnetic layer (upper) 41).

Generation of the thermal dispersion layer is not restricted to the dualspin-valve magnetoresistive thin film element shown in FIG. 5, but alsooccurs in the same manner with single spin-valve magnetoresistive thinfilm elements wherein the antiferromagnetic layer 11 is formed below thefree magnetic layer 16 (see FIG. 1), as well.

As described above, unless there is a certain degree of differencebetween the magnetic film thickness Ms·t_(P1) of the first pinnedmagnetic layers (lower) 32 and (upper) 43, and the magnetic filmthickness Ms·t_(P2) of the second pinned magnetic layers (lower) 34 and(upper) 41, the magnetization state does not easily achieve aFerri-state; on the other hand, if the difference between the magneticfilm thickness Ms·t_(P1) of the first pinned magnetic layers (lower) 32and (upper) 43, and the magnetic film thickness Ms·t_(P2) of the secondpinned magnetic layers (lower) 34 and (upper) 41 is too large, thisleads to undesirable deterioration in the exchange coupling magneticfield. Accordingly, with the present invention, as with the filmthickness ratio of the film thickness t_(P1) of the first pinnedmagnetic layer (lower) 32 and (upper) 43, and the film thickness t_(P2)of the second pinned magnetic layer (lower) 34 and (upper) 41, it ispreferable that (the magnetic film thickness Ms·t_(P1) of the firstpinned magnetic layers (lower) 32 and (upper) 43)/(the magnetic filmthickness Ms·t_(P2) of the second pinned magnetic layers (lower) 34 and(upper) 41) be in a range of 0.33 to 0.95, or in a range of 1.05 to 4.Also, with the present invention, it is preferable that the magneticfilm thickness Ms·t_(P1) of the first pinned magnetic layers (lower) 32and (upper) 43 and the magnetic film thickness Ms·t_(P2) of the secondpinned magnetic layers (lower) 34 and (upper) 41 be in a range of 10 to70 (ängström tesla), and that an absolute value obtained by subtractingthe magnetic film thickness Ms·t_(P2) of the second pinned magneticlayers (lower) 34 and (upper) 41 from the magnetic film thicknessMs·t_(P1) of the first pinned magnetic layers (lower) 32 and (upper) 43be equal to or greater than 2 (ängström tesla).

It is even more preferable that (the magnetic film thickness Ms·t_(P1)of the first pinned magnetic layers (lower) 32 and (upper) 43)/(themagnetic film thickness Ms t_(P2) of the second pinned magnetic layers(lower) 34 and (upper) 41) be in a range of 0.53 to 0.95 or 1.05 to 1.8.Also, in the above ranges, it is preferable that the magnetic filmthickness Ms·t_(P1) of the first pinned magnetic layers (lower) 32 and(upper) 43 and the magnetic film thickness Ms·t_(P2) of the secondpinned magnetic layers (lower) 34 and (upper) 41 be in a range of 10 to50 (ängström tesla), and that an absolute value obtained by subtractingthe magnetic film thickness Ms·t_(P2) of the second pinned magneticlayers (lower) 34 and (upper) 41 from the magnetic film thicknessMs·t_(P1) of the first pinned magnetic layers (lower) 32 and (upper) 43be equal to or greater than 2 (ängström tesla).

The nonmagnetic intermediate layers 33 and 42 introduced between thefirst pinned magnetic layers (lower) 32 and (upper) 43 and the secondpinned magnetic layers (lower) 34 and (upper) 41 shown in FIG. 5 arepreferably formed of one of the following; or of an alloy of two or morethereof: Ru, Rh, Ir, Cr, Re, and Cu.

As shown in FIG. 5, the film thickness value of the nonmagneticintermediate layer (lower) 33 formed below the free magnetic layer 36 ispreferably in the range of 3.6 to 9.6 ängström. Within this range, anexchange coupling magnetic field (Hex) of 500 (Oe) or greater can beobtained.

It is further preferable that the film thickness value of thenonmagnetic intermediate layer (lower) 33 be in the range of 4 to 9.4ängström. Within this range, an exchange coupling magnetic field of atleast 1,000 (Oe) or greater can be obtained.

Also, with the present invention, as shown in FIG. 5, the film thicknessvalue of the nonmagnetic intermediate layer (upper) 42 formed above thefree magnetic layer 36 is preferably in the range of 2.5 to 6.4 ängströmor 6.8 to 10.7 ängström. Within this range, an exchange couplingmagnetic field (Hex) of at least 500 (Oe) or greater can be obtained.

Further, with the present invention, it is further preferable that thefilm thickness value of the nonmagnetic intermediate layer (upper) 42 bein the range of 2.8 to 6.2 ängström or 6.8 to 10.3 ängström. Within thisrange, an exchange coupling magnetic field of at least 1,000 (Oe) orgreater can be obtained.

Also, a thickness of at least 100 ängström or greater for theantiferromagnetic layers 31 and 44 can obtain an exchange couplingmagnetic field of 500 (Oe) or greater. Further, the thickness of atleast 110 ängström or greater can obtain an exchange coupling magneticfield of 1,000 (Oe) or greater.

With known arrangements, the antiferromagnetic layers 31 and 44 areformed to a thickness of at least 200 ängström or greater. However,according to the present invention, the antiferromagnetic layers 31 and44 can be formed at half the thickness, so, with the particular case ofdual spin-valve magnetoresistive thin film elements wherein twoantiferromagnetic layers 31 and 44 are formed, the overall thickness ofthe spin-valve magnetoresistive thin film element can be reduced byaround 200 ängström or more. With such spin-valve magnetoresistive thinfilm elements that have been reduced in thickness, the gap length G1 canbe reduced even if the lower gap layer 121 and upper gap layer 125 shownin FIG. 13 are made to be thick enough to maintain sufficientinsulation, so as to deal with high-density recording.

By appropriately adjusting the film thickness ratio and film thicknessesof the first pinned magnetic layer (lower) 32 and (upper) 43, and thesecond pinned magnetic layer (lower) 34 and (upper) 41, the filmthickness of the nonmagnetic intermediate layers (lower) 33 and (upper)42, and the film thickness of the antiferromagnetic layers 31 and 44within the above-described ranges, ΔMR around the same as with knownarrangements can be obtained; specifically, ΔMR around 10% or more canbe obtained.

As shown in FIG. 5, the film thickness t_(P1) of the first pinnedmagnetic layer (lower) 32 formed below the free magnetic layer 36 isformed so as to be thinner than the film thickness t_(P2) of the secondpinned magnetic layer (upper) 34 formed with the nonmagneticintermediate layer 33 introduced therebetween. On the other hand, thefilm thickness t_(P1) of the first pinned magnetic layer (upper) 43formed above the free magnetic layer 36 is formed so as to be thickerthan the film thickness t_(P2) of the second pinned magnetic layer(upper) 41 formed with the nonmagnetic intermediate layer 42 introducedtherebetween. The magnetization of both first pinned magnetic layers(lower) 32 and (upper) 43 are magnetized in the direction opposite tothe direction Y in the Figure, and the magnetization of the secondpinned magnetic layers (lower) 34 and (upper) 41 are magnetized in thedirection Y in the Figure.

In the cases of the single spin-valve magnetoresistive thin filmelements shown in FIGS. 1 and 3, the film thickness and the like isadjusted so that the Ms·t_(P1) of the first pinned magnetic layer andthe Ms·t_(P2) of the second pinned magnetic layer differ, and thedirection of the magnetization of the first pinned magnetic layer may beeither in the direction of Y in the Figure, or in the direction oppositeto the direction of Y.

However, with the dual spin-valve magnetoresistive thin film elementshown in FIG. 5, there is the need to have the magnetization of thefirst pinned magnetic layers (lower) 32 and (upper) 43 both in the samedirection. Thus, with the present invention, the magnetic momentMs·t_(P1) of the first pinned magnetic layers (lower) 32 and (upper) 43is appropriately adjusted with the magnetic moment Ms·t_(P2) of thesecond pinned magnetic layers (lower) 34 and (upper) 41, and thedirection and magnitude of the magnetic field applied during thermaltreatment is appropriately set.

Now, the reason that the magnetization of the first pinned magneticlayers (lower) 32 and (upper) 43 are both directed in the same directionis in order to direct the magnetization of the second pinned magneticlayers (lower) 34 and (upper) 41 which come into an antiparallel statewith the magnetization of the first pinned magnetic layers (lower) 32and (upper) 43 in the same direction, and the reason thereof will bedescribed next.

As described above, the ΔMR of spin-valve magnetoresistive thin filmelements is obtained from the relationship between the pinned magnetismof the pinned magnetic layer, and the fluctuating magnetization of thefree magnetic layer. However, if the pinned magnetic layer is dividedinto a first pinned magnetic layer and second pinned magnetic layer aswith the present invention, the pinned magnetic layer which directlycontributes to the ΔMR is the second pinned magnetic layer, and thefirst pinned magnetic layer serves a supplementary role in pining themagnetization of the second pinned magnetic layer in a constantdirection.

For instance, if the magnetization of the second pinned magnetic layers(lower) 34 and (upper) 41 shown in FIG. 5 are pinned in a mutuallyopposing manner, resistance would be very small due to the relationshipbetween the pinned magnetization of the second pinned magnetic layer(lower) 34 and the fluctuating magnetization of the free magnetic layer36, even if the resistance due to the relationship between the pinnedmagnetization of the second pinned magnetic layer (upper) 41 and thefluctuating magnetization of the free magnetic layer 36 for example, islarge, so consequently, the ΔMR in the dual spin-valve magnetoresistivethin film element would be smaller than the ΔMR of the single spin-valvemagnetoresistive thin film element shown in FIGS. 1 and 3.

This problem is not limited to dual spin-valve magnetoresistive thinfilm elements wherein the pinned magnetic layer is divided into twolayers with a nonmagnetic intermediate layer introduced therebetween aswith the present invention, but also is the same for known dualspin-valve magnetoresistive thin film elements. Thus there is the needto pin the pinned magnetic layers formed above and below the freemagnetic layer in the same direction, in order to exhibit the propertiesof dual spin-valve magnetoresistive thin film elements which are capableof producing greater ΔMR than single spin-valve magnetoresistive thinfilm elements and obtaining greater output.

Now, with the present invention, as shown in FIG. 5, the pinned magneticlayer formed below the free magnetic layer 36 is arranged such that theMs·t_(P2) of the second pinned magnetic layer (lower) 34 is greater thanthe Ms·t_(P1) of the first pinned magnetic layer (lower) 32, and themagnetization of the second pinned magnetic layer (lower) 34 with thegreater Ms·t_(P2) is pinned in the direction Y in the Figure. Here, theso-called synthesized magnetic moment obtained by adding the Ms·t_(P2)of the second pinned magnetic layer 34 and the Ms·t_(P1) of the firstpinned magnetic layer 32 is dominated by the magnetic moment of thesecond pinned magnetic layer 34 with the greater Ms·t_(P2), and isdirected in the direction Y in the Figure.

On the other hand, the pinned magnetic layer formed above the freemagnetic layer 36 is arranged such that the Ms·t_(P1) of the firstpinned magnetic layer (upper) 43 is greater than the Ms·t_(P2) of thesecond pinned magnetic layer (upper) 41, and the magnetization of thefirst pinned magnetic layer (upper) 43 with the greater Ms·t_(P1) ispinned in the direction opposite to the direction Y in the Figure.

Here, the so-called synthesized magnetic moment obtained by adding theMs·t_(P1) of the first pinned magnetic layer (upper) 43 and theMs·t_(P2) of the second pinned magnetic layer (upper) 41 is dominated bythe Ms·t_(P1) of the first pinned magnetic layer (upper) 43, and isdirected in the direction opposite to the direction Y in the Figure.

That is to say, with the dual spin-valve magnetoresistive thin filmelement shown in FIG. 5, the directions of the synthesized magneticmoments which can be obtained by adding the Ms·t_(P1) of the firstpinned magnetic layer and the Ms·t_(P2) of the second pinned magneticlayer are opposite above and below the free magnetic layer 36. Thesynthesized magnetic moment directed in the direction Y in the Figurewhich is formed below the free magnetic layer 36, and the synthesizedmagnetic moment directed opposite to the direction Y in the Figure whichis formed above the free magnetic layer 36 together form a magneticfield turning in the left-hand direction in the Figure.

Accordingly, the magnetization of the first pinned magnetic layers(lower) 32 and (upper) 43, and the magnetization of the second pinnedmagnetic layers (lower) 34 and (upper) 41 can be maintained in an evenmore stable Ferri-state, owing to the magnetic field formed by the abovesynthesized magnetic moment.

Further, the sensing current 114 flows with the nonmagnetic electricallyconductive layers 35 and 39 as the center of the flow thereof. Causingthe sensing current 114 to flow forms a sensing current magnetic fielddue to the corkscrew rule, and causing the sensing current 114 to flowin the direction shown in FIG. 5 causes the direction of the sensingcurrent magnetic field created by the sensing current at the portion ofthe first pinned magnetic layer (lower) 32/nonmagnetic intermediatelayer (lower) 33/second pinned magnetic layer (lower) 34 that has beenformed below the free magnetic layer 36, to match the direction of thesynthesized magnetic moment of the first pinned magnetic layer (lower)32/nonmagnetic intermediate layer (lower) 33/second pinned magneticlayer (lower) 34, and further causes the direction of the sensingcurrent magnetic field created by the sensing current at the portion ofthe first pinned magnetic layer (upper) 43/nonmagnetic intermediatelayer (upper) 42/second pinned magnetic layer (upper) 41 that has beenformed above the free magnetic layer 36, to match the direction of thesynthesized magnetic moment of the first pinned magnetic layer (upper)43/nonmagnetic intermediate layer (upper) 42/second pinned magneticlayer (upper) 41.

Though the advantages of matching the direction of the sensing currentmagnetic field and the direction of the synthesized magnetic moment willbe described later in detail, it can be briefly stated that theadvantages are very great, since the thermal stability of the pinnedmagnetic layers can be increased, and a large sensing current can beused, so reproduction output can be improved. This is because theserelationships between the direction of the sensing current magneticfield and of the synthesized magnetic moment owe to the fact that thesynthesized magnetic moments of the pinned magnetic layers formed aboveand below the free magnetic layer 36 form the magnetic field turning inthe left-hand direction in the Figure.

Environment temperatures in devices now reach around 200° C., and thetrend is for the environment temperatures to further increase, due toincreases in revolutions of the recording medium, sensing currents, andso forth. Such increases in environment temperatures causes the exchangecoupling magnetic field to drop. However, according to the presentinvention, the magnetic field formed by the synthesized magnetic momentand the sensing current magnetic field allow the magnetization of thefirst pinned magnetic layers (lower) 32 and (upper) 43, and themagnetization of the second pinned magnetic layers (lower) 34 and(upper) 41, to be maintained in a thermally stable Ferri-state.

The above-described formation of the magnetic field owing to thesynthesized magnetic moment, and the directional relationship betweenthe magnetic field owing to the synthesized magnetic moment and thesensing current magnetic field, are configurations which are unique tothe present invention, and cannot be obtained with known dual spin-valvemagnetoresistive thin film elements which have pinned magnetic layersformed above and below a free magnetic layer in single layers andmagnetized and pinned in the same direction.

Next, the direction and magnitude of the magnetic field to be appliedduring thermal treatment will be described. With the spin-valvemagnetoresistive thin film element shown in FIG. 5, an antiferromagneticmaterial such as a PtMn alloy or the like which requires thermaltreatment is used as the antiferromagnetic layers 31 and 44 forgenerating an exchange coupling magnetic field (exchange anisotropicmagnetic field) at the interface between the first pinned magneticlayers (lower) 32 and (upper) 43 and the antiferromagnetic layers 31 and44. Thus, if the direction and magnitude of the magnetic field appliedduring thermal treatment is not appropriately controlled, themagnetization direction of the first pinned magnetic layers (lower) 32and (upper) 43 and second pinned magnetic layers (lower) 34 and (upper)41 cannot be obtained in a direction such as shown in FIG. 5.

First, in the stage of forming the films, as shown in FIG. 5, the Mst_(P1) of the first pinned magnetic layer (lower) 32 formed below thefree magnetic layer 36 is made to be smaller than the Ms t_(P1) of thesecond pinned magnetic layer (lower) 34, and also the Ms t_(P1) of thefirst pinned magnetic layer (upper) 43 formed above the free magneticlayer 36 is made to be greater than the MS t_(P2) of the second pinnedmagnetic layer (upper) 41.

As shown in FIG. 5, in the event that the first pinned magnetic layers(lower) 32 and (upper) 43 are to be directed in the direction oppositeto the direction Y in the Figure, referring to the above Tables 1 and 2shows that there is the need to apply a magnetic field of 5 k(Oe) orgreater (see Table 1 (4) and Table 2 (4)) in the direction opposite tothe direction Y in the Figure.

Applying a magnetic field of 5 k(Oe) or greater in the directionopposite to the direction Y in the Figure causes the magnetization ofthe first pinned magnetic layers (lower) 32 and (upper) 43, and themagnetization of the second pinned magnetic layers (lower) 34 and(upper) 41 to all be temporarily directed in the direction opposite tothe direction Y. The first pinned magnetic layers (lower) 32 and (upper)43 are pinned in the direction opposite to the direction Y by theexchange coupling magnetic field (exchange anisotropic magnetic field)generated at the interface between the first pinned magnetic layers(lower) 32 and (upper) 43 and the antiferromagnetic layers 31 and 44,and removing the magnetic field of 5 k(Oe) or greater causes themagnetization of the second pinned magnetic layers (lower) 34 and(upper) 41 to be inverted in the direction Y in the Figure due to theexchange coupling magnetic field (RKKY interaction) with the firstpinned magnetic layers (lower) 32 and (upper) 43, and be pinned in thedirection Y.

Alternatively, a magnetic field of 5 k(Oe) or greater may be applied inthe direction Y in the Figure. In this case, the magnetization of thefirst pinned magnetic layers (lower) 32 and (upper) 43 and themagnetization of the second pinned magnetic layers (lower) 34 and(upper) 41 to be magnetized opposite to the magnetization directionsshown in FIG. 5, thereby forming a magnetic field from right-handrotating synthesized magnetic moment.

Also, with the present invention, the Ms·t_(P1) of the first pinnedmagnetic layer (lower) 32 formed below the free magnetic layer 36 may bemade to be greater than the Ms·t_(P2) of the second pinned magneticlayer 34, and also the Ms·t_(P1) of the first pinned magnetic layer 43formed above the free magnetic layer 36 may be made to be smaller thanthe Ms·t_(P2) of the second pinned magnetic layer 41. In this case aswell, applying a magnetic field of 5 k(Oe) or greater in the directionregarding which magnetization of the first pinned magnetic layers(lower) 32 and (upper) 43 is desired, i.e., in the Y direction shown inthe Figure or in the opposite direction, thereby directing and pinningthe second pinned magnetic layers (lower) 34 and (upper) 41 formed aboveand below the free magnetic layer 36 in the same direction, and furtherforming a magnetic field from right-hand rotating or left-hand rotatingsynthesized magnetic moment.

It should be noted that directing the magnetization of the second pinnedmagnetic layers (lower) 34 and (upper) 41 formed above and below thefree magnetic layer 36 in the same direction, and further forming amagnetic field with synthesized magnetic moment and forming thedirectional relationship between the magnetic field owing to thesynthesized magnetic moment and the sensing current magnetic field,cannot be realized by any method other than that described above.

Now, other methods described below could be used to direct themagnetization of the second pinned magnetic layers (lower) 34 and(upper) 41 in the same direction. However, the synthesized magneticmoment formed above and below the free magnetic layer 36 would be facingin the same direction, so a magnetic field could not be formed with thesynthesized magnetic moment. However, the dual spin-valvemagnetoresistive thin film element according to the present invention iscapable of obtaining ΔMR of around the same as known dual spin-valvemagnetoresistive thin film elements with the following thermal treatmentas well, and further, the magnetization state of the pinned magneticlayers (first pinned magnetic layer and second pinned magnetic layer)can be maintained in a thermally stable state.

First, if the Ms·t_(P1) of the first pinned magnetic layer (lower) 32formed below the free magnetic layer 36 and the Ms·t_(P1) of the firstpinned magnetic layer (upper) 43 formed above the free magnetic layer 36are both made to be greater than the Ms·t_(P2) of the second pinnedmagnetic layers (lower) 34 and (upper) 41, applying a magnetic field of100 (Oe) to 1 k(Oe) or 5 k(Oe) or greater in the direction that themagnetization of the first pinned magnetic layers (lower) 32 and (upper)43 are to be directed directs both of the first pinned magnetic layers(lower) 32 and (upper) 43 in the same direction, and the magnetizationof both of the second pinned magnetic layers (lower) 34 and (upper) 41to be magnetized in an antiparallel manner with the magnetization of thefirst pinned magnetic layers (lower) 32 and (upper) 43 is directed andpinned in the same direction, due to the exchange coupling magneticfield (RKKY interaction) with the first pinned magnetic layers (lower)32 and (upper) 43.

Alternatively, if the Ms·t_(P1) of the first pinned magnetic layer(lower) 32 formed below the free magnetic layer 36 and the Ms·t_(P1) ofthe first pinned magnetic layer (upper) 43 formed above the freemagnetic layer 36 are both made to be smaller than the Ms·t_(P2) of thesecond pinned magnetic layers (lower) 34 and (upper) 41, applying amagnetic field of 100 (Oe) to 1 k(Oe) or 5 k(Oe) or greater in thedirection opposite to the direction that the first pinned magneticlayers (lower) 32 and (upper) 43 are to be directed directs both of thefirst pinned magnetic layers (lower) 32 and (upper) 43 in the samedirection, and the magnetization of both of the second pinned magneticlayers (lower) 34 and (upper) 41 to be magnetized in an antiparallelmanner with the magnetization of the first pinned magnetic layers(lower) 32 and (upper) 43 is directed and pinned in the same direction,due to the exchange coupling magnetic field (RKKY interaction) with thefirst pinned magnetic layers (lower) 32 and (upper) 43.

In this way, according to the spin-valve magnetoresistive thin filmelements shown in FIGS. 1 through 6, a pinned magnetic layer is dividedinto the two layers of a first pinned magnetic layer and a second pinnedmagnetic layer with a nonmagnetic intermediate layer introducedtherebetween, and the magnetization of the two layers is placed in anantiparallel state (Ferri-state) by the exchange coupling magnetic field(RKKY interaction) generated between the two pinned magnetic layers,thereby maintaining the magnetization state of the pinned magneticlayers in a state more thermally stable than that of known arrangements.

Particularly, the present invention uses as the antiferromagnetic layera PtMn alloy which exhibits high blocking temperature and generates alarge exchange coupling magnetic field (exchange anisotropic magneticfield) at the interface between the first pinned magnetic layer and theantiferromagnetic layer, so the magnetization state of the first pinnedmagnetic layer and the second pinned magnetic layer can be maintained ina further thermally stable manner.

Also, with the present invention, forming the film thickness ratiobetween the first pinned magnetic layer and the second pinned magneticlayer, the film thickness of the nonmagnetic intermediate layerintroduced between the first pinned magnetic layer and the second pinnedmagnetic layer, and the film thickness of the antiferromagnetic layer inan appropriate range enables a greater exchange coupling magnetic field(Hex) to be obtained. Accordingly, the thermal stability of the pinnedmagnetization of the first pinned magnetic layer and the second pinnedmagnetic layer can be further improved.

Further, forming the film thickness ratio between the film thicknesst_(P1) of the first pinned magnetic layer and the film thickness t_(P2)of the second pinned magnetic layer, and the film thicknesses of thefirst pinned magnetic layer, the second pinned magnetic layer, thenonmagnetic intermediate layer, and the antiferromagnetic layer, in anappropriate range, enables ΔMR around that of known arrangements to beobtained.

Further, with the present invention, in the event of using as theantiferromagnetic layer an antiferromagnetic material such as a PtMnalloy or the like which requires thermal treatment for generating anexchange coupling magnetic field (exchange anisotropic magnetic field)at the interface between the first pinned magnetic layer and theantiferromagnetic layer, forming the Ms t_(P1) of the first pinnedmagnetic layer and the Ms t_(P2) of the second pinned magnetic layer atdifferent values, and appropriately adjusting the magnitude anddirection of the magnetic field applied during thermal treatment enablesthe magnetization of the first pinned magnetic layer (and the secondpinned magnetic layer) to be magnetized in the desired direction.

Particularly, with the dual spin-valve magnetoresistive thin filmelement shown in FIG. 5, appropriately adjusting the Ms·t_(p1) of thefirst pinned magnetic layers (lower) 32 and (upper) 43, and theMs·t_(P2) of the second pinned magnetic layers (lower) 34 and (upper)41, and further appropriately adjusting the magnitude and direction ofthe magnetic field applied during thermal treatment enables themagnetization of both of the second pinned magnetic layers (lower) 34and (upper) 41 formed above and below the free magnetic layer 36 to bepinned in the same direction, and the synthesized magnetic momentsformed above and below the free magnetic layer 36 to be formed inmutually opposing directions, thereby forming a magnetic field with thesynthesized magnetic moment and forming the directional relationshipwith the magnetic field due to the synthesized magnetic moment and thesensing current magnetic field, consequently further improving thethermal stability of the magnetization of the pinned magnetic layers.

FIG. 7 is a side cross-sectional view schematically showing thestructure of a spin-valve magnetoresistive thin film element accordingto a fourth embodiment of the present invention, and FIG. 8 is across-sectional view of the spin valve magnetoresistive thin filmelement shown in FIG. 7, viewed from the side facing the recordingmedium.

As with the spin-valve magnetoresistive thin film elements shown inFIGS. 1 through 6, this spin-valve magnetoresistive thin film elementalso is provided to the trailing edge or the like of a floating sliderprovided in a hard disk drive, for detecting recorded magnetic fields onthe hard disk or the like. Now, the direction of motion of the magneticrecording medium such as a hard disk is in the Z direction as shown inthe Figure, and the direction of leaking magnetic field from themagnetic recording medium is in the Y direction.

Not only is the pinned magnetic layer in this spin-valvemagnetoresistive thin film element divided into two layers, but also thefree magnetic layer is divided into the two layers of a first freemagnetic layer and second free magnetic layer, with a nonmagneticintermediate layer introduced therebetween.

As shown in FIGS. 7 and 8, the spin-valve magnetoresistive thin filmelement comprises from the bottom: a base layer 50, antiferromagneticlayer 51, first pinned magnetic layer 52, nonmagnetic intermediate layer53, second pinned magnetic layer 54, nonmagnetic electrically conductivelayer 55, first free magnetic layer 56, nonmagnetic intermediate layer59, second free magnetic layer 60, and protective layer 61, in thatorder.

The base layer 50 and protective layer 61 are formed of Ta, for example,also, the antiferromagnetic layer 51 is preferably formed of a PtMnalloy, for example. PtMn alloys have better corrosion-resistantproperties than NiMn alloys or FeMn alloys conventionally used forantiferromagnetic layers, the blocking temperature is high, and a largeexchange coupling magnetic field can be obtained. Also, with the presentinvention, X—Mn alloys (wherein X is one or a plurality of the followingelements: Pd, Ir, Rh, Ru, Os) or PtMn—X alloys (wherein X is one or aplurality of the following elements: Pd, Ir, Rh, Ru, Os, Au, Ag) may beused instead of PtMn alloys.

The first pinned magnetic layer 52 and second pinned magnetic layer 54are comprised of Co film, an NiFe alloy, Co—Fe alloy, Co—Ni alloy,Co—NiFe alloy, or the like. The nonmagnetic intermediate layer 53 ispreferably formed of one of the following; or of an alloy of two or morethereof: Ru, Rh, Ir, Cr, Re, and Cu. Further, the nonmagneticelectrically conductive layer 55 is formed of Cu or the like.

The magnetization of the first pinned magnetic layer 52 and themagnetization of the second pinned magnetic layer 54 are in aFerri-state wherein each is magnetized in a manner antiparallel with theother, with the magnetization of the first pinned magnetic layer 52being pinned in the direction Y shown in the Figure, and themagnetization of the second pinned magnetic layer 54 in the directionopposite to Y. A large exchange coupling magnetic field is necessary tomaintain the stability of this Ferri-state, and with the presentinvention, the following various types of optimization are performed inorder to obtain a greater exchange coupling magnetic field.

With the spin-valve magnetoresistive thin film element shown in FIGS. 7and 8, (the thickness t_(P1) of the first pinned magnetic layer 52)/(thethickness t_(P2) of the second pinned magnetic layer 54) preferably isin a range of 0.33 to 0.95, or in a range of 1.05 to 4, and morepreferably is in a range of 0.53 to 0.95, or in a range of 1.08 to 1.8.

It is preferable that the film thickness of the first pinned magneticlayer 52 and the film thickness of the second pinned magnetic layer 54be in a range of 10 to 70 ängström, and also the film thickness t_(P1)of the first pinned magnetic layer 52 minus the film thickness t_(P2) ofthe second pinned magnetic layer 54|≧2 ängström. It is even morepreferable to be in a range of 10 to 50 ängström, and also the filmthickness t_(P1) of the first pinned magnetic layer 52 minus the filmthickness t_(P2) of the second pinned magnetic layer 54|≧2 ängström.

As described above, unless there is a certain degree of differencebetween the magnetic film thickness Ms·t_(P1) of the first pinnedmagnetic layer 52 and the magnetic film thickness Ms·t_(P2) of thesecond pinned magnetic layer 54, the magnetization state does not easilyachieve a Ferri-state. On the other hand, if the difference between themagnetic film thickness Ms·t_(P1) of the first pinned magnetic layer 52and the magnetic film thickness Ms·t_(P2) of the second pinned magneticlayer 54 is too great, this leads to undesirable deterioration in theexchange coupling magnetic field. Accordingly, with the presentinvention, as with the film thickness ratio between the film thicknesst_(P1) of the first pinned magnetic layer 52 and the film thicknesst_(P2) of the second pinned magnetic layer 54, it is preferable that(the magnetic film thickness Ms t_(P1) of the first pinned magneticlayer 52)/(the magnetic film thickness Ms·t_(P2) of the second pinnedmagnetic layer 54) be in a range of 0.33 to 0.95, or in a range of 1.05to 4. Also, with the present invention, it is preferable that themagnetic film thickness Ms·t_(P1) of the first pinned magnetic layer 52and the magnetic film thickness Ms·t_(P2) of the second pinned magneticlayer 54 be in a range of 10 to 70 (ängström tesla), and that anabsolute value obtained by subtracting the magnetic film thicknessMs·t_(P2) of the second pinned magnetic layer 54 from the magnetic filmthickness Ms·t_(P1) of the first pinned magnetic layer 52 is equal to orgreater than 2 (ängström tesla).

It is even more preferable that (the magnetic film thickness Ms·t_(P1)of the first pinned magnetic layer 52)/(the magnetic film thicknessMs·t_(P2) of the second pinned magnetic layer 54) be in a range of 0.53to 0.95 or in a range of 1.05 to 1.8. Also, in the above ranges, it ispreferable that the magnetic film thickness Ms·t_(P1) of the firstpinned magnetic layer 52 and the magnetic film thickness Ms·t_(P2) ofthe second pinned magnetic layer 54 be in a range of 10 to 50 (ängströmtesla), and that an absolute value obtained by subtracting the magneticfilm thickness Ms·t_(P2) of the second pinned magnetic layer 54 from themagnetic film thickness Ms·t_(P1) of the first pinned magnetic layer 52is equal to or greater than 2 (ängström tesla).

Also, it is preferable that the film thickness of the nonmagneticintermediate layer 53 introduced between the first pinned magnetic layer52 and second pinned magnetic layer 54 be in the range of 3.6 to 9.6ängström. Within this range, an exchange coupling magnetic field of 500(Oe) or greater can be obtained. It is further preferable for this to bein the range of 4 to 9.4, since an exchange coupling magnetic field of1,000 (Oe) or greater can be obtained.

Also, a thickness of at least 90 ängström or greater for theantiferromagnetic layer 51 is preferable, since it can obtain anexchange coupling magnetic field of 500 (Oe) or greater. Furtherpreferable is a thickness of at least 100 ängström or greater, which canobtain an exchange coupling magnetic field of 1,000 (Oe) or greater.

The first free magnetic layer 56 is formed on the nonmagneticelectrically conductive layer 55 shown in FIGS. 7 and 8. As shown inFIGS. 7 and 8, the first free magnetic layer 56 is formed of two layers,with a Co film 57 being formed on the side coming into contact with thenonmagneticelectrically conductive layer 55. The reason that the Co film57 is formed on the side in contact with the nonmagnetic electricallyconductive layer 55 is that firstly, a greater ΔMR can be obtained, andsecondly that dispersion with the electrically conductive layer 55 canbe prevented.

An NiFe alloy film 58 is formed on the Co film 57. Further formed on theNiFe alloy film 58 is a nonmagnetic intermediate layer 59. Formed on thenonmagnetic intermediate layer 59 is the second free magnetic layer 60,and further formed on the second free magnetic layer 60 is theprotective layer 61 formed of Ta or the like.

The second free magnetic layer 60 is comprised of a Co film, an NiFealloy, Co—Fe alloy, Co—NiFe alloy, or the like.

The spin-valve film from the base layer 50 through the protective layer61 shown in FIG. 8 has the sides thereof inclined, so the spin-valvefilm is formed in the shape of a trapezoid. Hard magnetic bias layers 62and electrically conductive layers 63 are formed on either side of thespin-valve film. The hard magnetic bias layers 62 are formed of a Co—Ptalloy, Co—Cr—Pt alloy, etc., and the electrically conductive layers 63are formed of Cu, Cr, or the like.

A nonmagnetic intermediate layer 59 is introduced between the first freemagnetic layer 56 and second free magnetic layer 60 shown in FIGS. 7 and8, so the magnetization of the first free magnetic layer 56 and themagnetization of the second free magnetic layer 60 are in a mutuallyantiparallel state (Ferri-state), due to an exchange coupling magneticfield (RKKY interaction) generated between the first free magnetic layer56 and second free magnetic layer 60.

With the spin-valve magnetoresistive thin film element shown in FIG. 8,for example, the film thickness t_(F1) of the first free magnetic layer56 is made to be smaller than the film thickness t_(F2) of the secondfree magnetic layer 60, and also the Ms·t_(F1) of the first freemagnetic layer 56 is made to be smaller than the Ms·t_(F2) of the secondfree magnetic layer 60. If a bias magnetic field is applied from thehard magnetic bias layers 62 in the direction X in the Figures, themagnetization of the second free magnetic layer 60 with the greaterMs·t_(F2) is affected by the bias magnetic field so as to be aligned inthe direction X in the Figure, and the magnetization of the first freemagnetic layer 56 with the smaller Ms·t_(F1) is in a direction oppositeto X in the Figure, due to the exchange coupling magnetic field (RKKYinteraction) generated between the first free magnetic layer 56 andsecond free magnetic layer 60.

In the event that an external magnetic field intrudes from the directionY in the Figure, the magnetization of the first free magnetic layer 56and second free magnetic layer 60 maintains the Ferri-state, and at thesame time rotates due to being affected by the external magnetic field.Then, electrical resistance changes owing to the relationship betweenthe fluctuating magnetism of the first free magnetic layer 56 whichcontributes to the ΔMR and the pinned magnetism of the second pinnedmagnetic layer 54 (magnetized in the direction opposite to Y in theFigures, for example), thereby detecting the signals of the externalmagnetic field.

With the present invention, the film thickness ratio between the filmthickness t_(F1) of the first free magnetic layer 56 and the filmthickness t_(F2) of the second free magnetic layer 60 is optimized,thereby allowing an even greater exchange coupling magnetic field to beobtained, and at the same time, allowing ΔMR around the same as withknown arrangements to be obtained.

With the present invention, (the film thickness t_(F1) of the first freemagnetic layer 56/the film thickness t_(F2) of the second free magneticlayer 60) is preferably in a range of 0.56 to 0.83 or 1.25 to 5. Withinthis range, an exchange coupling magnetic field of 500 (Oe) or greatercan be obtained. With the present invention, (the film thickness t_(F1)of the first free magnetic layer 56/the film thickness t_(F2) of thesecond free magnetic layer 60) is even more preferably in a range of0.61 to 0.83 or 1.25 to 2.1. Within this range, an exchange couplingmagnetic field of 1,000 (Oe) or greater can be obtained.

The reason that the range of 0.83 to 1.25 has been excluded for (thefilm thickness t_(F1) of the first free magnetic layer 56/the filmthickness t_(F2) of the second free magnetic layer 60) is that in theevent that the film thickness t_(F1) of the first free magnetic layer 56and the magnetic film thickness t_(F2) of the second free magnetic layer60 are formed to approximately the same value, and that the Ms·t_(F1) ofthe first free magnetic layer 56 and the Ms·t_(F2) of the second freemagnetic layer 60 are formed to approximately the same value, themagnetization of both the first free magnetic layer 56 and second freemagnetic layer 60 are affected by the bias magnetic field from the hardmagnetic bias layer 62, and attempt to turn in the direction of thatbias magnetic field. Consequently, the magnetization of each of both thefirst free magnetic layer 56 and second free magnetic layer 60 do notachieve an antiparallel state, and a stable magnetization state cannotbe maintained.

Also, unless there is a certain degree of difference between themagnetic film thickness Ms·t_(F1) of the first free magnetic layer 56and the magnetic film thickness Ms·t_(F2) of the second free magneticlayer 60, the magnetization state does not easily achieve a Ferri-state.On the other hand, if the difference between the magnetic film thicknessMs·t_(F1) of the first free magnetic layer 56 and the magnetic filmthickness Ms·t_(F1) of the second free magnetic layer 60 is too great,this leads to undesirable deterioration in the exchange couplingmagnetic field. Accordingly, with the present invention, as with thefilm thickness ratio between the film thickness t_(F1) of the first freemagnetic layer 56 and the film thickness t_(F2) of the second freemagnetic layer 60, it is preferable that (the magnetic film thicknessMs·t_(F1) of the first free magnetic layer 56)/(the magnetic filmthickness Ms·t_(F2) of the second free magnetic layer 60) be in a rangeof 0.56 to 0.83, or in a range of 1.25 to 5. It is further preferablewith the present invention that (the magnetic film thickness Ms·t_(F1)of the first free magnetic layer 56)/(the magnetic film thicknessMs·t_(F2) of the second free magnetic layer 60) be in a range of 0.61 to0.83, or in a range of 1.25 to 2.1.

Also, with the present invention, the nonmagnetic intermediate layer 59introduced between the first free magnetic layer 56 and the second freemagnetic layer 60 is preferably formed of one of the following; or of analloy of two or more thereof: Ru, Rh, Ir, Cr, Re, and Cu. Further, it ispreferable that the film thickness of the nonmagnetic intermediate layer59 be in the range of 5.5 to 10.0 ängström. Within this range, anexchange coupling magnetic field of 500 (Oe) or greater can be obtained.It is even more preferable for the film thickness of the nonmagneticintermediate layer 59 to be in the range of 5.9 to 9.4 ängström, sincean exchange coupling magnetic field of 1,000 (Oe) or greater can beobtained.

Adjusting the film thickness ratio of the first pinned magnetic layer 52and the second pinned magnetic layer 54, the film thickness of both thenonmagnetic intermediate layer 53 and antiferromagnetic layer 51, thefilm thickness ratio of the first free magnetic layer 56 and the secondfree magnetic layer 60, and the film thickness of the nonmagneticintermediate layer 59, within the above value ranges, allows a ΔMR (rateof resistance change) around that obtained by known arrangements to beobtained.

Next, the method of thermal treatment will be described. With thespin-valve magnetoresistive thin film element shown in FIGS. 7 and 8, anantiferromagnetic material which generates an exchange coupling magneticfield (exchange anisotropic magnetic field) at the interface between thefirst pinned magnetic layer 52 and the antiferromagnetic layer 51 isused, such as subjecting a PtMn alloy to thermal treatment. Accordingly,there is the need to appropriately control the direction and magnitudeof the magnetic field applied in the thermal treatment, so as to adjustthe direction of magnetization of the first pinned magnetic layer 52 andthe second pinned magnetic layer 54.

For instance, if the Ms·t_(P1) of the first pinned magnetic layer 52 isgreater than the Ms·t_(P2) of the second pinned magnetic layer 54, amagnetic field of 100 (Oe) to 1 k(Oe), or 5 k(Oe) should be applied inthe direction that the magnetization of the first pinned magnetic layer52 is to be directed. For example, if the first pinned magnetic layer 52is to be directed in the direction Y shown in the Figures, a magneticfield of 100 (Oe) to 1 k(Oe) is applied in the direction Y. The firstpinned magnetic layer 52 with the great Ms t_(P1) is directed in thedirection of the magnetic field, i.e., in the direction Y, and themagnetization of the first pinned magnetic layer 52 is pinned in thedirection Y in the Figure, due to the exchange coupling magnetic field(exchange anisotropic magnetic field) generated at the interface betweenthe first pinned magnetic layer 52 and the antiferromagnetic layer 51.On the other hand, the magnetization of the second pinned magnetic layer54 is pinned in the direction opposite to Y in the Figure, due to theexchange coupling magnetic field (RKKY interaction) generated betweenthe first pinned magnetic layer 52 and second pinned magnetic layer 54or, a magnetic field of 5 k(Oe) or greater is applied in the directionY. This exchange coupling magnetic field (RKKY interaction) between thefirst pinned magnetic layer 52 and second pinned magnetic layer 54 isaround 1 k(Oe) to 5 k(Oe), so applying a magnetic field of 5 k(Oe) orgreater causes the magnetization of the first pinned magnetic layer 52and the magnetization of the second pinned magnetic layer 54 to be bothdirected in the direction Y. At this time, the magnetization of thefirst pinned magnetic layer 52 is pinned in the direction Y, due to theexchange coupling magnetic field (exchange anisotropic magnetic field)generated at the interface between the first pinned magnetic layer 52and the antiferromagnetic layer 51. On the other hand, at the time thatthe magnetic field of 5 k(Oe) or greater is removed, the magnetizationof the second pinned magnetic layer 54 is directed and pinned in theopposite direction to Y in the Figure, by the exchange coupling magneticfield (RKKY interaction) between the first pinned magnetic layer 52 andsecond pinned magnetic layer 54.

Alternatively, if the Ms·t_(P1) of the first pinned magnetic layer 52 issmaller than the Ms·t_(P2) of the second pinned magnetic layer 54, amagnetic field of 100 (Oe) to 1 k(Oe) should be applied in the directionopposite to the direction in which the magnetization of the first pinnedmagnetic layer 52 is to be directed, or a magnetic field of 5 k(Oe) orgreater should be applied in the direction that the magnetization of thefirst pinned magnetic layer 52 is to be directed. For example, if thefirst pinned magnetic layer 52 is to be directed in the direction Yshown in the Figures, a magnetic field of 100 (Oe) to 1 k(Oe) is appliedin the direction opposite to Y. Accordingly, the second pinned magneticlayer 54 with the great Ms·t_(P2) is directed in the direction of themagnetic field, i.e., in the direction opposite to Y, and themagnetization of the first pinned magnetic layer 52 is directed in thedirection Y in the Figure, due to the exchange coupling magnetic field(RKKY interaction) between the first pinned magnetic layer 52 and secondpinned magnetic layer 54. The magnetization of the first pinned magneticlayer 52 is pinned in the Y direction due to the exchange couplingmagnetic field (exchange anisotropic magnetic field) generated at theinterface between the first pinned magnetic layer 52 and theantiferromagnetic layer 51, and the magnetization of the second pinnedmagnetic layer 54 is pinned in the direction opposite to Y in theFigure. Or, a magnetic field of 5 k(Oe) or greater is applied in thedirection Y. Applying a magnetic field of 5 k(Oe) or greater causes themagnetization of the first pinned magnetic layer 52 and themagnetization of the second pinned magnetic layer 54 to be both directedin the direction Y, and the magnetization of the first pinned magneticlayer 52 to be pinned in the direction Y, due to the exchange couplingmagnetic field (exchange anisotropic magnetic field) generated at theinterface between the first pinned magnetic layer 52 and theantiferromagnetic layer 51. At the time that the magnetic field of 5k(Oe) or greater is removed, the magnetization of the second pinnedmagnetic layer 54 which had been directed in the direction Y, isdirected and pinned in the opposite direction to Y in the Figure, by theexchange coupling magnetic field (RKKY interaction) between the firstpinned magnetic layer 52 and second pinned magnetic layer 54.

Also, with the present invention, with the direction X and direction Yin the Figure as the positive direction, and with the direction oppositeto X and the direction opposite to Y in the Figure as the negativedirection, it is preferable that the absolute value of the so-calledsynthesized magnetic moment obtained by adding the Ms·t_(F1) of thefirst free magnetic layer 56 and the Ms·t_(F2) of the second freemagnetic layer 60 be greater than the absolute value of the synthesizedmagnetic moment obtained by adding the Ms·t_(P1) of the first pinnedmagnetic layer 52 and the Ms·t_(P2) of the second pinned magnetic layer54. That is to say, |(Ms·t_(F1)+Ms·t_(F2))/(Ms·t_(P1)+Ms·t_(P2))|>1 isdesirable.

An arrangement wherein the absolute value of the synthesized magneticmoment of the first free magnetic layer 56 and second free magneticlayer 60 is greater than the absolute value of the synthesized magneticmoment of the first pinned magnetic layer 52 and second pinned magneticlayer 54 has the advantages that the magnetization of the first freemagnetic layer 56 and second free magnetic layer 60 is not easilyaffected by the synthesized magnetic moment of the first pinned magneticlayer 52 and second pinned magnetic layer 54, and the magnetization ofthe first free magnetic layer 56 and second free magnetic layer 60rotates with higher sensitivity of external magnetic fields, therebyenabling increases in output.

FIG. 9 is a side cross-sectional view schematically showing thestructure of a spin-valve magnetoresistive thin film element accordingto a fifth embodiment of the present invention, and FIG. 10 is across-sectional view of the spin-valve magnetoresistive thin filmelement shown in FIG. 9, viewed from the side facing the recordingmedium.

This spin-valve magnetoresistive thin film element has been formed byreversing the order of layers in the spin valve magnetoresistive thinfilm element shown in FIGS. 7 and 8.

That is, the spin-valve magnetoresistive thin film element comprisesfrom the bottom: a base layer 70, second free magnetic layer 71,nonmagnetic intermediate layer 72, first free magnetic layer 73,nonmagnetic electrically conductive layer 76, second pinned magneticlayer 77, nonmagnetic intermediate layer 78, first pinned magnetic layer79, antiferromagnetic layer 80, and protective layer 81, in that order.

The base layer 70 and protective layer 81 are formed of Ta or the like.The antiferromagnetic layer 80 is preferably formed of a PtMn alloy.PtMn alloys have better corrosion-resistant properties than NiMn alloysor FeMn alloys conventionally used for antiferromagnetic layers, theblocking temperature is high, and a large exchange coupling magneticfield can be obtained. Also, with the present invention, X—Mn alloys(wherein X is one or a plurality of the following elements: Pd, Ir, Rh,Ru, Os) or PtMn—X alloys (wherein X is one or a plurality of thefollowing elements: Pd, Ir, Rh, Ru, Os, Au, Ag) may be used instead ofPtMn alloys.

The first pinned magnetic layer 79 and second pinned magnetic layer 77are comprised of Co film, an NiFe alloy, Co—Fe alloy, Co—Ni alloy,Co—NiFe alloy, or the like. Also, the nonmagnetic intermediate layer 78is preferably formed of one of the following; or of an alloy of two ormore thereof: Ru, Rh, Ir, Cr, Re, and Cu. Further, the nonmagneticelectrically conductive layer 76 is formed of Cu or the like.

With the spin-valve magnetoresistive thin film element shown in FIGS. 9and 10, (the thickness t_(P1) of the first pinned magnetic layer79)/(the thickness t_(P2) of the second pinned magnetic layer 77)preferably is in a range of 0.33 to 0.95, or in a range of 1.05 to 4,and that the film thickness t_(P1) of the first pinned magnetic layer 79and the film thickness t_(P2) of the second pinned magnetic layer 77both be in a range of 10 to 70 ängström, and also that |the filmthickness t_(P1) of the first pinned magnetic layer 79 minus the filmthickness t_(P2) of the second pinned magnetic layer 77|≧2 ängström.Appropriate adjustment within these ranges enables an exchange couplingmagnetic field of 500 (Oe) or greater to be obtained.

Further, with the present invention, (the film thickness t_(P1) of thefirst pinned magnetic layer 79)/(the film thickness t_(P2) of the secondpinned magnetic layer 77) is even more preferably in a range of 0.53 to0.95, or in a range of 1.05 to 1.8, and the film thickness t_(P1) of thefirst pinned magnetic layer 79 and the film thickness t_(P2) of thesecond pinned magnetic layer 77 both are even more preferably in a rangeof 10 to 50 ängström, with |the film thickness t_(P1) of the firstpinned magnetic layer 79 minus the film thickness t_(P2) of the secondpinned magnetic layer 77|≧2 ängström. Appropriate adjustment withinthese ranges enables an exchange coupling magnetic field of 1,000 (Oe)or greater to be obtained.

As described above, unless there is a certain degree of differencebetween the magnetic film thickness Ms·t_(P1) of the first pinnedmagnetic layer 79 and the magnetic film thickness Ms·t_(P2) of thesecond pinned magnetic layer 77, the magnetization state does not easilyachieve a Ferri-state. On the other hand, if the difference between themagnetic film thickness Ms·t_(P1) of the first pinned magnetic layer 79and the magnetic film thickness Ms·t_(P2) of the second pinned magneticlayer 77 is too great, this leads to undesirable deterioration in theexchange coupling magnetic field. Accordingly, with the presentinvention, as with the film thickness ratio of the film thickness t_(P1)of the first pinned magnetic layer 79 and the film thickness t_(P2) ofthe second pinned magnetic layer 77, it is preferable that (the magneticfilm thickness Ms·t_(P1) of the first pinned magnetic layer 79)/(themagnetic film thickness Ms·t_(P2) of the second pinned magnetic layer77) be in a range of 0.33 to 0.95, or in a range of 1.05 to 4. Also,with the present invention, it is preferable that the magnetic filmthickness Ms·t_(P1) of the first pinned magnetic layer 79 and themagnetic film thickness Ms·t_(P2) of the second pinned magnetic layer 77be in a range of 10 to 70 (ängström tesla), and that an absolute valueobtained by subtracting the magnetic film thickness Ms·t_(P2) of thesecond pinned magnetic layer 77 from the magnetic film thicknessMs·t_(P1) of the first pinned magnetic layer 79 is equal to or greaterthan 2 (ängström tesla).

It is even more preferable that (the magnetic film thickness Ms t_(P1)of the first pinned magnetic layer 79)/(the magnetic film thicknessMs·t_(P2) of the second pinned magnetic layer 77) be in a range of 0.53to 0.95 or in a range of 1.05 to 1.8. Also, in the above ranges, it ispreferable that the magnetic film thickness Ms·t_(P1) of the firstpinned magnetic layer 79 and the magnetic film thickness Ms·t_(P2) ofthe second pinned magnetic layer 77 be in a range of 10 to 50 (ängströmtesla), and that an absolute value obtained by subtracting the magneticfilm thickness Ms·t_(P2) of the second pinned magnetic layer 77 from themagnetic film thickness Ms·t_(P1) of the first pinned magnetic layer 79is equal to or greater than 2 (ängström tesla).

Also, it is preferable that the film thickness of the nonmagneticintermediate layer 78 introduced between the first pinned magnetic layer79 and second pinned magnetic layer 77 be in the range of 2.5 to 6.4, or6.6 to 10.7 ängström. Within this range, an exchange coupling magneticfield of 500 (Oe) or greater can be obtained. It is further preferablefor this to be in the range of 2.8 to 6.2 ängström or 6.8 to 10.3ängström, since an exchange coupling magnetic field of 1,000 (Oe) orgreater can be obtained.

Also, a thickness of 90 ängström or greater for the antiferromagneticlayer 80 is preferable. An exchange coupling magnetic field of 500 (Oe)or greater can be obtained within this range. Further preferable is athickness of 100 ängström or greater, whereby an exchange couplingmagnetic field of 1,000 (Oe) or greater can be obtained within thisrange.

With the spin-valve magnetoresistive thin film element shown in FIG. 10,the free magnetic layer is divided and formed of two layers, with afirst free magnetic layer 73 being formed on the side coming intocontact with the nonmagnetic electrically conductive layer 76, and theother free magnetic layer comprising the second free magnetic layer 71.As shown in FIG. 10, the first free magnetic layer 73 is formed of twolayers, with a the film 75 formed on the side coming into contact withthe nonmagnetic electrically conductive layer 76 being formed of a Cofilm. The layer 74 formed on the side coming into contact with thenonmagnetic intermediate layer 72, and the second free magnetic layer 71are comprised of, e.g., an NiFe alloy, Co—Fe alloy, Co—Ni alloy, Co—NiFealloy, or the like.

The spin-valve film from the base layer 70 through the protective layer81 shown in FIG. 10 has the sides thereof inclined, so the spin-valvefilm is formed in the shape of a trapezoid. Hard magnetic bias layers 82and electrically conductive layers 83 are formed on either side of thespin valve film. The hard magnetic bias layers 82 are formed of a Co—Ptalloy, Co—Cr—Pt alloy, etc., and the electrically conductive layers 83are formed of Cu, Cr, or the like.

A nonmagnetic intermediate layer 72 is introduced between the first freemagnetic layer 73 and second free magnetic layer 71 shown in FIG. 10, sothe magnetism of the first free magnetic layer 73 and the magnetism ofthe second free magnetic layer 71 are in a mutually antiparallel state(Ferri-state), due to an exchange coupling magnetic field (RKKYinteraction) generated between the first free magnetic layer 73 andsecond free magnetic layer 71. With the spin-valve magnetoresistive thinfilm element shown in FIG. 10, the film thickness t_(F1) of the firstfree magnetic layer 73 is made to be greater than the film thicknesst_(F2) of the second free magnetic layer 71, and also the Ms·t_(F1) ofthe first free magnetic layer 73 is made to be greater than theMs·t_(F2) of the second free magnetic layer 71, so in the event that abias magnetic field is applied from the hard magnetic bias layers 82 inthe direction X in the Figures, the magnetization of the first freemagnetic layer 73 with the greater Ms·t_(F1) is affected by the biasmagnetic field so as to be aligned in the direction X in the Figure, andthe magnetization of the second free magnetic layer 71 with the smallerMs·t_(F2) is in a direction opposite to X in the Figure, due to theexchange coupling magnetic field (RKKY interaction) generated betweenthe first free magnetic layer 73 and second free magnetic layer 71.Also, with the present invention, film thickness t_(F1) of the firstfree magnetic layer 73 may be made to be smaller than the film thicknesst_(F2) of the second free magnetic layer 71, and also the Ms·t_(F1) ofthe first free magnetic layer 73 may be made to be smaller than theMs·t_(F2) of the second free magnetic layer 71.

In the event that an external magnetic field intrudes from the directionY in the Figure, the magnetization of the first free magnetic layer 73and second free magnetic layer 71 maintains the Ferri-state, and at thesame time rotates due to being affected by the external magnetic field.Then, electrical resistance changes owing to the relationship betweenthe magnetization direction of the first free magnetic layer 73 whichcontributes to the ΔMR and the pinned magnetization of the second pinnedmagnetic layer 71, thereby detecting the signals of the externalmagnetic field.

With the present invention, the film thickness ratio between the filmthickness t_(F1) of the first free magnetic layer 73 and the filmthickness t_(F2) of the second free magnetic layer 71 is optimized,thereby allowing an even greater exchange coupling magnetic field to beobtained, and at the same time, allowing ΔMR around the same as withknown arrangements to be obtained.

With the present invention, (the film thickness t_(F1) of the first freemagnetic layer 73/the film thickness t_(F1) of the second free magneticlayer 71) is preferably in a range of 0.56 to 0.83 or 1.25 to 5. Withinthis range, an exchange coupling magnetic field of 500 (Oe) or greatercan be obtained. Also with the present invention, (the film thicknesst_(F1) of the first free magnetic layer 73/the film thickness t_(F2) ofthe second free magnetic layer 71) is even more preferably in a range of0.61 to 0.83 or 1.25 to 2.1. Within this range, an exchange couplingmagnetic field of 1,000 (Oe) or greater can be obtained.

Also, unless there is a certain degree of difference between themagnetic film thickness Ms·t_(F1) of the first free magnetic layer 73and the magnetic film thickness Ms·t_(F2) of the second free magneticlayer 71, the magnetization state does not easily achieve a Ferri-state.On the other hand, if the difference between the magnetic film thicknessMs·t_(F1) of the first free magnetic layer 73 and the magnetic filmthickness Ms·t_(F2) of the second free magnetic layer 71 is too great,this leads to undesirable deterioration in the exchange couplingmagnetic field. Accordingly, with the present invention, as with thefilm thickness ratio between the film thickness t_(F1) of the first freemagnetic layer 73 and the film thickness t_(F2) of the second freemagnetic layer 71, it is preferable that (the magnetic film thicknessMs·t_(F1) of the first free magnetic layer 73)/(the magnetic filmthickness Ms·t_(F2) of the second free magnetic layer 71) be in a rangeof 0.56 to 0.83, or in a range of 1.25 to 5. It is further preferablewith the present invention that (the magnetic film thickness Ms·t_(F1)of the first free magnetic layer 73)/(the magnetic film thicknessMs·t_(F2) of the second free magnetic layer 71) be in a range of 0.61 to0.83, or in a range of 1.25 to 2.1.

Also, with the present invention, the nonmagnetic intermediate layer 72introduced between the first free magnetic layer 73 and the second freemagnetic layer 71 is preferably formed of one of the following; or of analloy of two or more thereof: Ru, Rh, Ir, Cr, Re, and Cu. Further, it ispreferable that the film thickness of the nonmagnetic intermediate layer72 be in the range of 5.5 to 10.0 ängström. Within this range, anexchange coupling magnetic field of 500 (Oe) or greater can be obtained.It is even more preferable for the film thickness of the nonmagneticintermediate layer 72 to be in the range of 5.9 to 9.4 ängström. Withinthis range, an exchange coupling magnetic field of 1,000 (Oe) or greatercan be obtained.

Adjusting the film thickness ratio of the first pinned magnetic layer 79and the second pinned magnetic layer 77, the film thickness of thenonmagnetic intermediate layer 78 and antiferromagnetic layer 80, thefilm thickness ratio of the first free magnetic layer 73 and the secondfree magnetic layer 71, and the film thickness of the nonmagneticintermediate layer 72, so as to be within the above ranges, allows a ΔMR(rate of resistance change) around that obtained by known arrangementsto be obtained.

Next, the method of thermal treatment will be described. For instance,if the Ms·t_(P1) of the first pinned magnetic layer 79 is greater thanthe Ms·t_(P2) of the second pinned magnetic layer 77, a magnetic fieldof 100 (Oe) to 1 k(Oe), or 5 k(Oe) should be applied in the directionthat the magnetization of the first pinned magnetic layer 79 is to bedirected. Alternatively, if the Ms·t_(P1) of the first pinned magneticlayer 79 is smaller than the Ms·t_(P2) of the second pinned magneticlayer 77, a magnetic field of 100 (Oe) to 1 k(Oe) should be applied inthe direction opposite to the direction in which the magnetization ofthe first pinned magnetic layer 79 is to be directed, or a magneticfield of 5 k(Oe) or greater should be applied in the direction that themagnetization of the first pinned magnetic layer 79 is to be directed.In the present invention, the magnetization of the first pinned magneticlayer 79 is pinned in the Y direction, and the magnetization of thesecond pinned magnetic layer 77 is pinned in the direction opposite to Yin the Figure. Or, the magnetization of the first pinned magnetic layer79 is pinned in the direction opposite to Y, and the magnetization ofthe second pinned magnetic layer 77 is pinned in the direction Y in theFigure.

Also, with the present invention, with the direction X and direction Yin the Figure as the positive direction, and with the direction oppositeto X and the direction opposite to Y in the Figure as the negativedirection, it is preferable that the absolute value of the so-calledsynthesized magnetic moment obtained by adding the Ms·t_(F1) of thefirst free magnetic layer 73 and the Ms t_(F2) of the second freemagnetic layer 71 be greater than the absolute value of the synthesizedmagnetic moment obtained by adding the Ms·t_(P1) of the first pinnedmagnetic layer 79 and the Ms·t_(P2) of the second pinned magnetic layer77. That is to say, |(Ms·t_(F1)+Ms·t_(F2))/(Ms·t_(P1)+Ms·t_(P2))|>1 isdesirable.

An arrangement wherein the absolute value of the synthesized magneticmoment of the first free magnetic layer 73 and second free magneticlayer 71 is greater than the absolute value of the synthesized magneticmoment of the first pinned magnetic layer 79 and second pinned magneticlayer 77 has the advantages that the magnetization of the first freemagnetic layer 79 and second free magnetic layer 77 is not easilyaffected by the synthesized magnetic moment of the first pinned magneticlayer 79 and second pinned magnetic layer 77, and the magnetization ofthe first free magnetic layer 73 and second free magnetic layer 71rotates with higher sensitivity of external magnetic fields, therebyenabling increases in output.

FIG. 11 is a side cross-sectional view illustrating the structure of aspin-valve magnetoresistive thin film element according to a sixthembodiment of the present invention, and FIG. 12 is a cross-sectionalview of the spin-valve magnetoresistive thin film element shown in FIG.11, viewed from the side facing the recording medium;

This spin-valve magnetoresistive thin film element is a so-called dualspin-valve magnetoresistive thin film element comprising nonmagneticelectrically conductive layers, pinned magnetic layers, andantiferromagnetic layers formed above and below a free magnetic layer asthe center thereof, with the free magnetic layers and pinned magneticlayers each being divided into two layers with nonmagnetic intermediatelayers introduced therebetween.

The bottom-most layer shown in FIGS. 11 and 12 is a base layer 91, andformed on this base layer 91 are the following layers in order from thebottom up: an antiferromagnetic layer 92, first pinned magnetic layer(lower) 93, nonmagnetic intermediate layer (lower) 94, second pinnedmagnetic layer (lower) 95, nonmagnetic electrically conductive layer 96,second free magnetic layer 97, nonmagnetic intermediate layer 100, firstfree magnetic layer 101, nonmagnetic electrically conductive layer 104,second pinned magnetic layer (upper) 105, nonmagnetic intermediate layer(upper) 106, first pinned magnetic layer (upper) 107, antiferromagneticlayer 108, and protective layer 109.

First, description will be given regarding materials. It is preferablethat the antiferromagnetic layers 92 and 108 be formed of a PtMn alloy.PtMn alloys have better corrosion-resistant properties than NiMn alloysor FeMn alloys conventionally used for antiferromagnetic layers, theblocking temperature is high, and a large exchange coupling magneticfield (exchange anisotropic magnetic field) can be obtained. Also, withthe present invention, X—Mn alloys (wherein X is one or a plurality ofthe following elements: Pd, Ir, Rh, Ru, Os) or PtMn—X′ alloys (whereinX, is one or a plurality of the following elements: Pd, Ir, Rh, Ru, Os,Au, Ag) may be used instead of the PtMn alloys.

The first pinned magnetic layers (lower) 93 and (upper) 107, and secondpinned magnetic layers (lower) 95 and (upper) 105 are comprised of a Cofilm, an NiFe alloy, Co—Fe alloy, Co—Ni alloy, Co—NiFe alloy, or thelike. Also, the nonmagnetic intermediate layers (lower) 94 and (upper)106, formed between the first pinned magnetic layers (lower) 93 and(upper) 107, and second pinned magnetic layers (lower) 95 and (upper)105, and the nonmagnetic intermediate layer 100 formed between the firstfree magnetic layer 101 and second free magnetic layer 97, arepreferably formed of one of the following; or of an alloy of two or morethereof: Ru, Rh, Ir, Cr, Re, and Cu. Further, the nonmagneticelectrically conductive layers 96 and. 104 formed of Cu or the like.

As shown in FIG. 11, the first free magnetic layer 101 and the secondfree magnetic layer 97 are comprised of two layers. The layer 103 of thefirst free magnetic layer 101, and the layer 98 of the second freemagnetic layer 97, formed to the side coming into contact with thenonmagnetic electrically conductive layers 96 and 104, are formed of Cofilms. Also, the layer 102 of the first free magnetic layer 101, and thelayer 99 of the second free magnetic layer 97, with the nonmagneticintermediate layer 100 introduced therebetween, are formed of an NiFealloy, Co—Fe alloy, Co Ni alloy, Co—NiFe alloy, or the like.

Forming the layers 98 and 103 at the side coming into contact with thenonmagnetic electrically conductive layers 96 and 104 of Co films allowsa greater ΔMR to be obtained, and also prevents dispersion of thenonmagnetic electrically conductive layers 96 and 104.

Next, the appropriate ranges for the film thickness of each layer willbe described. It is preferable that the film thickness ratio between thefilm thickness t_(P1) of the first pinned magnetic layer (lower) 93 andthe film thickness t_(P2) of the second pinned magnetic layer (lower) 95formed below the free magnetic layer, and the film thickness ratiobetween the film thickness t_(P1) of the first pinned magnetic layer(upper) 107 and the film thickness t_(P2) of the second pinned magneticlayer (upper) 105 formed above the free magnetic layer be such wherein(film thickness t_(P1) of first pinned magnetic layer (lower) 93 and(upper) 107)/(film thickness t_(P2) of second pinned magnetic layer(lower) 95 and (upper) 105) is in a range of 0.33 to 0.95, or in a rangeof 1.05 to 4. Also, it is preferable that the film thickness of thefirst pinned magnetic layer (lower) 93 and (upper) 107, and the filmthickness of the second pinned magnetic layer (lower) 95 and (upper) 105be in a range of 10 to 70 ängström, and that |film thickness t_(P1) offirst pinned magnetic layers (lower) 93 and (upper) 107 minus filmthickness t_(P2) of second pinned magnetic layers (lower) 95 and (upper)105|≧2 ängström. In the above ranges, an exchange coupling magneticfield of 500 (Oe) or greater can be obtained.

It is also preferable with the present invention that the (filmthickness t_(P1) of first pinned magnetic layer (lower) 93, (upper)107)/(film thickness t_(P2) of second pinned magnetic layer (lower) 95,(upper) 105) be in a range of 0.53 to 0.95, or in a range of 1.05 to1.8, and moreover, that the film thickness t_(P1) of the first pinnedmagnetic layers (lower) 93 and (upper) 107, and the film thicknesst_(P2) of the second pinned magnetic layers (lower) 95 and (upper) 105,be in a range of 10 to 50 ängström, and that |film thickness t_(P1) offirst pinned magnetic layers (lower) 93 and (upper) 107 minus filmthickness t_(P2) of second pinned magnetic layers (lower) 95 and (upper)105|≧2 ängström. In these ranges, an exchange coupling magnetic field of1,000 (Oe) or greater can be obtained.

Further, as described above, with the present invention, anantiferromagnetic material is used for the antiferromagnetic layers 92and 108, such as a PtMn alloy or the like which requires thermaltreatment for generating an exchange coupling magnetic field (exchangeanisotropic magnetic field) at the interface between the first pinnedmagnetic layers (lower) 93 and (upper) 107 and the antiferromagneticlayers 92 and 108.

However, dispersion of metal elements easily occurs at the interfacebetween the antiferromagnetic layer 92 formed below the free magneticlayer and the first pinned magnetic layer (lower) 93, and a thermaldispersion layer is easily formed, so the magnetic layer serving as thefirst pinned magnetic layer (lower) 93 is thinner than the actual filmthickness t_(P1). Accordingly, in order to approximately equalize theexchange coupling magnetic field generated in the layers above the freemagnetic layer and the exchange coupling magnetic field generated in thelayers below the free magnetic layer, it is preferable that the (filmthickness t_(P1) of first pinned magnetic layer (lower) 93/filmthickness t_(P2) of second pinned magnetic layer (lower) 95) formedbelow the free magnetic layer be greater than the (film thickness t_(P1)of first pinned magnetic layer (upper) 107/film thickness t_(P2) ofsecond pinned magnetic layer (upper) 105) formed above the free magneticlayer. Equalizing the exchange coupling magnetic field generated in thelayers above the free magnetic layer and the exchange coupling magneticfield generated in the layers below the free magnetic layer reducesdeterioration of the exchange coupling magnetic field in themanufacturing process, and improves the reliability of the magnetichead.

As described above, unless there is a certain degree of differencebetween the magnetic film thickness Ms t_(P1) of the first pinnedmagnetic layers (lower) 93 and (upper) 107, and the magnetic filmthickness MS t_(P2) of the second pinned magnetic layers (lower) 95 and(upper) 105, the magnetization state does not easily achieve aFerri-state. On the other hand, in the event that the difference betweenthe magnetic film thickness Ms·t_(P1) of the first pinned magneticlayers (lower) 93 and (upper) 107, and the magnetic film thicknessMs·t_(P2) of the second pinned magnetic layers (lower) 95 and (upper)105 is too great, this leads to undesirable deterioration in theexchange coupling magnetic field. Accordingly, with the presentinvention, as with the film thickness ratio of the film thickness t_(P1)of the first pinned magnetic layer (lower) 93 and (upper) 107, and thefilm thickness t_(P2) of the second pinned magnetic layer (lower) 95 and(upper) 105, it is preferable that (the magnetic film thicknessMs·t_(P1), of the first pinned magnetic layers (lower) 93 and (upper)107)/(the magnetic film thickness Ms·t_(P2) of the second pinnedmagnetic layers (lower) 95 and (upper) 105) be in a range of 0.33 to0.95, or in a range of 1.05 to 4. Also, with the present invention, itis preferable that the magnetic film thickness Ms·t_(P1) of the firstpinned magnetic layers (lower) 93 and (upper) 107 and the magnetic filmthickness Ms t_(P2) of the second pinned magnetic layers (lower) 95 and(upper) 105 be in a range of 10 to 70 (ängström tesla), and that anabsolute value obtained by subtracting the magnetic film thicknessMs·t_(P2) of the second pinned magnetic layers (lower) 95 and (upper)105 from the magnetic film thickness Ms t_(P1) of the first pinnedmagnetic layers (lower) 93 and (upper) 107 be equal to or greater than 2(ängström tesla).

It is even more preferable that (the magnetic film thickness Ms·t_(P1)of the first pinned magnetic layers (lower) 93 and (upper) 107)/(themagnetic film thickness Ms·t_(P2) of the second pinned magnetic layers(lower) 95 and (upper) 105) be in a range of 0.53 to 0.95 or 1.05 to1.8. Also, in the above ranges, it is preferable that the magnetic filmthickness Ms·t_(P1) of the first pinned magnetic layers (lower) 93 and(upper) 107 and the magnetic film thickness Ms·t_(P2) of the secondpinned magnetic layers (lower) 95 and (upper) 105 be in a range of 10 to50 (ängström tesla), and that an absolute value obtained by subtractingthe magnetic film thickness Ms·t_(P2) of the second pinned magneticlayers (lower) 95 and (upper) 105 from the magnetic film thicknessMs·t_(P1) of the first pinned magnetic layers (lower) 93 and (upper) 107be equal to or greater than 2 (ängström tesla).

Also, with the present invention, the film thickness value of thenonmagnetic intermediate layer (lower) 94, introduced between the firstpinned magnetic layer (lower) 93 and second pinned magnetic layer(lower) 95 formed below the free magnetic layer, is preferably in therange of 3.6 to 9.6 ängström. Within this range, an exchange couplingmagnetic field of 500 (Oe) or greater can be obtained. It is furtherpreferable that this film thickness be in the range of 4 to 9.4ängström. Within this range, an exchange coupling magnetic field of atleast 1,000 (Oe) or greater can be obtained.

Also, the film thickness value of the nonmagnetic intermediate layer(upper) 106, introduced between the first pinned magnetic layer (upper)107 and second pinned magnetic layer (upper) 105 formed above the freemagnetic layer, is preferably in the range of 2.5 to 6.4 ängström, or inthe range of 6.6 to 10.7 ängström. Within this range, an exchangecoupling magnetic field of 500 (Oe) or greater can be obtained. It isfurther preferable that this film thickness be in the range of 2.8 to6.2 ängström, or in the range of 6.8 to 10.3 ängström. Within thisrange, an exchange coupling magnetic field of at least 1,000 (Oe) orgreater can be obtained.

Also, with the present invention, it is preferable that the thickness ofthe antiferromagnetic layers 92 and 108 be at least 100 ängström orgreater, since thickness of at least 100 ängström or greater for theantiferromagnetic layers 92 and 108 can obtain an exchange couplingmagnetic field of at least 500 (Oe) or greater. Further, with thepresent invention, a thickness of at least 110 ängström or greater forthe antiferromagnetic layers 92 and 108 can obtain an exchange couplingmagnetic field of 1,000 (Oe) or greater.

Also according to the present invention, with the film thickness of thefirst free magnetic layer 101 as t_(F1), and with the film thickness ofthe second free magnetic layer 97 as t_(F2), (the film thickness t_(F1)of the first free magnetic layer 101/the film thickness t_(F2) of thesecond free magnetic layer 97) is preferably in a range of 0.56 to 0.83or 1.25 to 5. Within this range, an exchange coupling magnetic field of500 (Oe) or greater can be obtained. Also, (the film thickness of thefirst free magnetic layer/the film thickness of the second free magneticlayer) is even more preferably in a range of 0.61 to 0.83 or 1.25 to2.1. Within this range, an exchange coupling magnetic field of 1,000(Oe) or greater can be obtained.

Also, unless there is a certain degree of difference between themagnetic film thickness Ms·t_(F1) of the first free magnetic layer 101and the magnetic film thickness Ms·t_(F2) of the second free magneticlayer 97, the magnetization state does not easily achieve a Ferri-state.On the other hand, if the difference between the magnetic film thicknessMs·t_(F1) of the first free magnetic layer 101 and the magnetic filmthickness Ms·t_(F2) of the second free magnetic layer 97 is too great,this leads to undesirable deterioration in the exchange couplingmagnetic field. Accordingly, with the present invention, as with thefilm thickness ratio between the film thickness t_(F1) of the first freemagnetic layer 101 and the film thickness t_(F2) of the second freemagnetic layer 97, it is preferable that (the magnetic film thicknessMs·t_(F1) of the first free magnetic layer 101)/(the magnetic filmthickness Ms·t_(F2) of the second free magnetic layer 97) be in a rangeof 0.56 to 0.83, or in a range of 1.25 to 5. It is further preferablewith the present invention that (the magnetic film thickness Ms·t_(F1)of the first free magnetic layer 101)/(the magnetic film thicknessMs·t_(F2) of the second free magnetic layer 97) be in a range of 0.61 to0.83, or in a range of 1.25 to 2.1.

Also, regarding the nonmagnetic intermediate layer 100 introducedbetween the first free magnetic layer 101 and the second free magneticlayer 97, it is preferable that the film thickness thereof be in therange of 5.5 to 10.0 ängström, since within this range, an exchangecoupling magnetic field of 500 (Oe) or greater can be obtained. It iseven more preferable for the film thickness of the nonmagneticintermediate layer 100 to be in the range of 5.9 to 9.4 ängström, sincean exchange coupling magnetic field of 1,000 (Oe) or greater can beobtained in these ranges.

According to the present invention, appropriately adjusting the filmthickness ratio of the first pinned magnetic layers (lower) 93 and(upper) 107 and the second pinned magnetic layers (lower) 95 and (upper)105; the film thickness of the first pinned magnetic layers (lower) 93and (upper) 107 and the second pinned magnetic layers (lower) 95 and(upper) 105, the nonmagnetic intermediate layers (lower) 94 and (upper)106, and antiferromagnetic layers 92 and 108; and further the filmthickness ratio of the first free magnetic layer 101 and the second freemagnetic layer 97; and the film thickness of the nonmagneticintermediate layer 100; so as to be in the above ranges, allows a ΔMRaround that obtained by known arrangements to be obtained.

Now, with the dual spin-valve magnetoresistive thin film element shownin FIGS. 11 and 12, the magnetization of each of the second pinnedmagnetic layers (lower) 95 and (upper) 105 formed above and below thefree magnetic layer need to be in mutually opposing directions. This isdue to the fact that the free magnetic layer is divided into the firstfree magnetic layer 101 and second free magnetic layer 97, and that themagnetization of the first free magnetic layer 101 and the magnetizationof the second free magnetic layer 97 are in an antiparallel state.

For example, as shown in FIGS. 11 and 12, if the magnetization of thefirst free magnetic layer 101 is magnetized in the opposite direction ofthe direction X in the Figures, the magnetization of the second freemagnetic layer 97 is in the state of being magnetized in the directionX. due to the exchange coupling magnetic field (RKKY interaction)between the first free magnetic layer 101 and second free magnetic layer97. The magnetization of the first free magnetic layer 101 and thesecond free magnetic layer 97 maintains a Ferri-state, but is invertedupon being affected by an external magnetic field.

With the dual spin-valve magnetoresistive thin film element shown inFIGS. 11 and 12, the magnetization of the first free magnetic layer 101and the second free magnetic layer 97 are both layers contributing tothe ΔMR, with electric resistance changing due to the relationshipbetween the fluctuating magnetization of the first free magnetic layer101 and the second free magnetic layer 97, and the pinned magnetism ofthe second pinned magnetic layers (lower) 95 and (upper) 105. In orderto exhibit the functions of the dual spin-valve magnetoresistive thinfilm element from which a greater ΔMR can be expected than with a singlespin-valve magnetoresistive thin film element, there is the need tocontrol the direction of the magnetization of the second pinned magneticlayers (lower) 95 and (upper) 105 so that the change in resistance ofthe first free magnetic layer 101 and second pinned magnetic layer(upper) 105, and the change in resistance of the second free magneticlayer 97 and second pinned magnetic layer (lower) 95, both demonstratethe same fluctuation. That is, the arrangement should be such that inthe event that the change in resistance of the first free magnetic layer101 and second pinned magnetic layer (upper) 105 reaches a maximumvalue, the change in resistance of the second free magnetic layer 97 andsecond pinned magnetic layer (lower) 95 also reaches a maximum value,and that in the event that the change in resistance of the first freemagnetic layer 101 and second pinned magnetic layer (upper) 105 reachesa minimum value, the change in resistance of the second free magneticlayer 97 and second pinned magnetic layer (lower) 95 also reaches aminimum value.

Accordingly, with the dual spin-valve magnetoresistive thin film elementshown in FIGS. 11 and 12, the magnetization of the first free magneticlayer 101 and the second free magnetic layer 97 are magnetized in anantiparallel manner. Thus, there is the need to magnetize themagnetization of the second pinned magnetic layer (upper) 105 and themagnetization of the second pinned magnetic layer (lower) 95 in mutuallyopposing directions.

In light of the above, with the present invention, the magnetization ofthe second pinned magnetic layer (upper) 105 and the magnetization ofthe second pinned magnetic layer (lower) 95 are pinned in opposingdirections. However, there is the need to appropriately adjust the Ms tof each pinned magnetic layer, and the direction and magnitude of themagnetic field applied during thermal treatment, in order to performsuch control of magnetization direction.

First, regarding the Ms·t of each pinned magnetic layer, it is necessarythat the Ms·t_(P1) of the first pinned magnetic layer (upper) 107 formedabove the free magnetic layer is made to be greater than the Ms·t_(P2)of the second pinned magnetic layer (upper) 105, and the Ms·t_(P1) ofthe first pinned magnetic layer (lower) 93 formed below the freemagnetic layer is made to be smaller than the Ms·t_(P2) of the secondpinned magnetic layer (lower) 95, or that the Ms·t_(P1) of the firstpinned magnetic layer (upper) 107 formed above the free magnetic layeris made to be smaller than the Ms·t_(P2) of the second pinned magneticlayer (upper) 105, and the Ms·t_(P1) of the first pinned magnetic layer(lower) 93 formed below the free magnetic layer is made to be greaterthan the Ms·t_(P2) of the second pinned magnetic layer (lower) 95.

With the present invention, an antiferromagnetic material is used forthe antiferromagnetic layers 92 and 108, such as a PtMn alloy or thelike which requires annealing (thermal treatment) in a magnetic fieldfor generating an exchange coupling magnetic field at the interfacebetween the first pinned magnetic layers (lower) 93 and (upper) 107 andthe antiferromagnetic layers 92 and 108, so the direction and magnitudeof the magnetic field applied during this thermal treatment must beappropriately adjusted. With the present invention, if the Ms·t_(P1) ofthe first pinned magnetic layer (upper) 107 formed above the freemagnetic layer is greater than the Ms·t_(P2) of the second pinnedmagnetic layer (upper) 105, and the Ms·t_(P1) of the first pinnedmagnetic layer (lower) 93 formed below the free magnetic layer issmaller than the Ms·t_(P2) of the second pinned magnetic layer (lower)95, a magnetic field of 100 (Oe) to 1 k(Oe) is applied in the directionin which the magnetization of the first pinned magnetic layer (upper)107 formed above the free magnetic layer is to be directed.

For example, as shown in FIG. 11, if the magnetization of the firstpinned magnetic layer (upper) 107 is to be directed in the direction Yin the Figure, a magnetic field of 100 (Oe) to 1 k(Oe) is applied in thedirection Y. At this point, the first pinned magnetic layer (upper) 107with the greater Ms·t_(P1), and the second pinned magnetic layer (lower)95 formed below the free magnetic layer are both turned in the directionof the applied magnetic field, i.e., the direction Y in the Figure. Onthe other hand, the magnetization of the second pinned magnetic layer(upper) 105 with the smaller Ms t_(P1) formed above the free magneticlayer is magnetized in a manner antiparallel with the magnetizationdirection of the first pinned magnetic layer (upper) 107, due to theexchange coupling magnetic field (RKKY interaction) between the secondpinned magnetic layer (upper) 105 and the first pinned magnetic layer(upper) 107. In the same way, the magnetization of the first pinnedmagnetic layer (lower) 93 with the smaller Ms t_(P2) formed below thefree magnetic layer attempts to attain a Ferri-state with themagnetization of the second pinned magnetic layer (lower) 95 and ismagnetized in the opposite direction to Y. The magnetization of thefirst pinned magnetic layer (upper) 107 formed above the free magneticlayer is pinned in the direction Y by means of the exchange couplingmagnetic field (exchange anisotropic magnetic field) generated at theinterface between the first pinned magnetic layer (upper) 107 and theantiferromagnetic layer 108 at the time of thermal treatment, and themagnetization of the second pinned magnetic layer (upper) 105 is pinnedin the opposite direction to Y. In the same way, magnetization of thefirst pinned magnetic layer (lower) 93 formed below the free magneticlayer is pinned in the direction opposite to Y by means of the exchangecoupling magnetic field (exchange anisotropic magnetic field), and themagnetization of the second pinned magnetic layer (lower) 95 is pinnedin the direction Y.

Also, if the Ms·t_(P1) of the first pinned magnetic layer (upper) 107formed above the free magnetic layer is made to be smaller than theMs·t_(P2) of the second pinned magnetic layer (upper) 105, and theMs·t_(P1) of the first pinned magnetic layer (lower) 93 formed below thefree magnetic layer is made to be greater than the Ms·t_(P2) of thesecond pinned magnetic layer (lower) 95, a magnetic field of 100 (Oe) to1 k(Oe) is applied in the direction in which the magnetization of thefirst pinned magnetic layer (lower) 93 formed below the free magneticlayer is to be directed.

In this way, magnetizing the second pinned magnetic layers (lower) 95and (upper) 105 formed above and below the free magnetic layer inopposite directions allows a ΔMR around that obtained by known dualspin-valve magnetoresistive thin film elements to be obtained.

Also, with the present invention, in order to arrange for themagnetization of the first free magnetic layer 101 and the magnetizationof the second free magnetic layer 97 which are in a Ferri-state to beinverted with better sensitivity to external magnetic fields, thesynthesized magnetic moment obtained by adding the magnetic moment ofthe first free magnetic layer 101 and the magnetic moment of the secondfree magnetic layer 97 should be greater than the synthesized magneticmoment obtained by adding the magnetic moment of the first pinnedmagnetic layer (lower) 93 and the magnetic moment of the second pinnedmagnetic layer (lower) 95 formed below the free magnetic layer, and thesynthesized magnetic moment obtained by adding the magnetic moment ofthe first pinned magnetic layer (upper) 107 and the magnetic moment ofthe second pinned magnetic layer (upper) 105 formed above the freemagnetic layer. That is to say, for example, with magnetic moments inthe direction X and direction Y in the Figure as the positive values,and with magnetic moments in the direction opposite to X and thedirection opposite to Y in the Figure as negative values, it ispreferable that the synthesized magnetic moment |Ms·t_(F1)+Ms·t_(F2)| begreater than the synthesized magnetic moment |Ms·t_(P1)+Ms·t_(P2)| ofthe first pinned magnetic layer (upper) 107 and the magnetic moment ofthe second pinned magnetic layer (upper) 105, and the synthesizedmagnetic moment |Ms·t_(P1)+Ms·t_(P2)| of the first pinned magnetic layer(lower) 93 and the second pinned magnetic layer (lower) 95.

As described above, with the spin-valve magnetoresistive thin filmelements shown in FIG. 7 through FIG. 12, not only are the pinnedmagnetic layers divided into two layers, but the free magnetic layer isdivided into a first free magnetic layer and second free magnetic layerwith a nonmagnetic intermediate layer introduced therebetween, and themagnetization of the two free magnetic layers is placed in anantiparallel state (Ferri-state) by the exchange coupling magnetic field(RKKY interaction) generated between the two free magnetic layers,thereby enabling the magnetization of the first free magnetic layer andsecond free magnetic layer to be inverted with good sensitivity toexternal magnetic fields.

Also, according to the present invention, forming the film thicknessratio of the first free magnetic layer and the second free magneticlayer, the film thickness of the nonmagnetic intermediate layerintroduced between the first free magnetic layer and the second freemagnetic layer, or the film thickness ratio of the first pinned magneticlayer and the second pinned magnetic layer, the nonmagnetic intermediatelayer introduced between the first pinned magnetic layer and the secondpinned magnetic layer, and the antiferromagnetic layers, so as to be inthe above ranges, increases the exchange coupling magnetic field. Themagnetization state of the first pinned magnetic layer and the secondpinned magnetic layer is pinned magnetization and the magnetizationstate of the first free magnetic layer and the second free magneticlayer is fluctuating magnetization, so a thermally stable Ferri-statecan be maintained, and further, a ΔMR around that obtained by knownarrangements can be obtained.

With the present invention, further adjusting the direction of thesensing current allows an even more thermally stable antiparallel state(Ferri-state) between the magnetization of the first pinned magneticlayer and the magnetization of the second pinned magnetic layer to bemaintained.

With spin-valve magnetoresistive thin, film elements, electricallyconductive layers are formed on either side of the layered structureformed of antiferromagnetic layers, pinned magnetic layers, nonmagneticelectrically conductive layers, and free magnetic layers, with sensingcurrent being caused to flow from these electrically conductive layers.The sensing current mainly flows through the low-resistance nonmagneticelectrically conductive layers, the interface between the nonmagneticelectrically conductive layers and pinned magnetic layers, and theinterface between the nonmagnetic electrically conductive layers andfree magnetic layers. With the present invention, the pinned magneticlayer is divided into a first pinned magnetic layer and second pinnedmagnetic layer, and the sensing current mainly flows over the interfacebetween the second pinned magnetic layer and nonmagnetic electricallyconductive layer.

Causing the sensing current to flow forms a sensing current magneticfield due to the corkscrew rule. With the present invention, thedirection in which the sensing current is caused to flow is adjusted sothat the direction of the sensing current magnetic field is the samedirection as that of the synthesized magnetic moment obtained by addingthe magnetic moment of the first pinned magnetic layer and the magneticmoment of the second pinned magnetic layer.

With the spin-valve magnetoresistive thin film element shown in FIG. 1,a second pinned magnetic layer 54 is formed below the nonmagneticelectrically conductive layer 15. In this case, the direction of thesensing current magnetic field is matched with the magnetizationdirection of the pinned magnetic layer with the greater magnetic moment(i.e., either the first pinned magnetic layer 52 or second pinnedmagnetic layer 54).

As shown in FIG. 1, the magnetic moment of the second pinned magneticlayer 54 is greater than the magnetic moment of the first pinnedmagnetic layer 52, and the magnetic moment of the second pinned magneticlayer 54 is in the direction opposite to Y in the Figure (i.e., to theleft direction in the Figure). Accordingly, the synthesized magneticmoment obtained by adding the magnetic moment of the first pinnedmagnetic layer 52 and the magnetic moment of the second pinned magneticlayer 54 is in the direction opposite to Y in the Figure (i.e., to theleft in the Figure).

As noted above, the nonmagnetic electrically conductive layer 15 isformed above the second pinned magnetic layer 54 and the first pinnedmagnetic layer 52. Accordingly, the direction in which the sensingcurrent 112 flows should be controlled such that the sensing currentmagnetic field, formed by the sensing current 112 which flows centrallyalong the nonmagnetic electrically conductive layer 15, is directed inthe left direction in the Figure below the nonmagnetic electricallyconductive layer 15, thus matching the direction of the synthesizedmagnetic moment of the first pinned magnetic layer 52 and the secondpinned magnetic layer 54, and the direction of the sensing currentmagnetic field.

As shown in FIG. 1, the sensing current 112 is caused to flow in thedirection X in the Figure, due to the corkscrew rule. The sensingcurrent magnetic field owing to the sensing current is formed so as toturn to the right as viewed in the Figure. Accordingly, a sensingcurrent magnetic field in the left direction in the Figure (opposite tothe direction Y) is applied to the layers below the nonmagneticelectrically conductive layer 15. This sensing current magnetic fieldacts to reinforce the synthesized magnetic moment, the exchange couplingmagnetic field (RKKY interaction) acting between the first pinnedmagnetic layer 52 and the second pinned magnetic layer 54 is amplified,and the antiparallel state between the magnetization of the first pinnedmagnetic layer 52 and the magnetization of the second pinned magneticlayer 54 can be further thermally stabilized.

Particularly, it is known that causing a sensing current of 1 mA to flowgenerates a sensing current magnetic field of approximately 30 (Oe), andfurther that the element temperature rises by about 15° C. Moreover, thenumber of revolutions of the recording medium speeds up to around 1,000rpm, and this increase in revolutions raises the temperature within thedevice to around 100° C. Accordingly, if a sensing current of 10 mA iscaused to flow, the temperature of the spin-valve magnetoresistive thinfilm element rises to about 250° C., and a great sensing currentmagnetic field of approximately 300 (Oe) is generated.

In an arrangement with such a very high environment temperature andgreat sensing current, the antiparallel state between the magnetizationof the first pinned magnetic layer 52 and the magnetization of thesecond pinned magnetic layer 54 easily collapses in the event that thedirection of the synthesized magnetic moment obtained by adding themagnetic moments of the first pinned magnetic layer 52 and the secondpinned magnetic layer 54, and the direction of the sensing currentmagnetic field, are opposed.

Also, besides adjusting the direction of the sensing current magneticfield, there is the need to use an antiferromagnetic material with ahigh blocking temperature as the antiferromagnetic layer 11 in order toendure high environment temperatures. Accordingly, the present inventionuses a PtMn alloy with a blocking temperature of approximately 400° C.

If the synthesized magnetic moment of the magnetic moment of the firstpinned magnetic layer 52 and the magnetic moment of the second pinnedmagnetic layer 54 shown in FIG. 1 is facing in the right direction inthe Figure, (i.e., in the direction Y), the sensing current should becaused to flow in the direction opposite to X in the Figure, so that thesensing current magnetic field is formed turning to the left as viewedin the Figure.

Next, description will be made regarding the sensing current directionof the spin-valve magnetoresistive thin film element shown in FIG. 3will be described.

In FIG. 3, the second pinned magnetic layer 25 and the first pinnedmagnetic layer 27 are formed above the nonmagnetic electricallyconductive layer 24. As shown in FIG. 3, the magnetic moment of thefirst pinned magnetic layer 27 is greater than the magnetic moment ofthe second pinned magnetic layer 25, and the direction of the magneticmoment of the first pinned magnetic layer 27 is in the direction Y(toward the right in the Figure). Accordingly, the direction of thesynthesized magnetic moment obtained by adding the magnetic moment ofthe first pinned magnetic layer 27 and the magnetic moment of the secondpinned magnetic layer 25 faces the right in the Figure.

As shown in FIG. 3, the sensing current 113 is caused to flow in thedirection X shown in the Figure. The sensing current magnetic fieldcreated due to the corkscrew rule by causing the sensing current 113 toflow turns to the right as viewed in the Figure. The second pinnedmagnetic layer 25 and the first pinned magnetic layer 27 are formedabove the nonmagnetic electrically conductive layer 24, so a sensingcurrent magnetic field intrudes into the second pinned magnetic layer 25and the first pinned magnetic layer 27 from the right direction in theFigure (the direction opposite to Y), so the direction matches that ofthe synthesized magnetic moment, and consequently, the antiparallelstate between the magnetization of the second pinned magnetic layer 25and the magnetization of the first pinned magnetic layer 27 does noteasily collapse.

If the synthesized magnetic moment is facing the left direction in theFigure (the direction opposite to Y), there is the need to cause thesensing current 113 to flow in the direction opposite to X, therebygenerating a sensing current magnetic field turning to the left asviewed in the Figure, thus aligning the direction of the synthesizedmagnetic moment of the first pinned magnetic layer 27 and the secondpinned magnetic layer 25.

The spin-valve magnetoresistive thin film element shown in FIG. 5 is adual spin-valve magnetoresistive thin film element wherein first pinnedmagnetic layers (lower) 32 and (upper) 43, and second pinned magneticlayers (lower) 34 and (upper) 41 are formed above and below the freemagnetic layer 36.

With this dual spin-valve magnetoresistive thin film element, there isthe need to control the direction and magnitude of the magnetic momentof the first pinned magnetic layers (lower) 32 and (upper) 43, and thedirection and magnitude of the magnetic moment of the second pinnedmagnetic layers (lower) 34 and (upper) 41, so that the synthesizedmagnetic moments formed above and below the free magnetic layer 36 aredirected in mutually opposing directions.

As shown in FIG. 5, the magnetic moment of the second pinned magneticlayer (lower) 34 formed below the free magnetic layer 36 is greater thanthe magnetic moment of the first pinned magnetic layer (lower) 32, andthe magnetic moment of the second pinned magnetic layer (lower) 34 isfacing the right in the Figure (direction Y in the Figure). Accordingly,the synthesized magnetic moment obtained by adding the magnetic momentof the first pinned magnetic layer (lower) 32 and the magnetic moment ofthe second pinned magnetic layer (lower) 34 is facing the right in theFigure (direction Y in the Figure). Also, the magnetic moment of thefirst pinned magnetic layer (upper) 43 formed above the free magneticlayer 36 is greater than the magnetic moment of the second pinnedmagnetic layer (upper) 41, and the magnetic moment of the first pinnedmagnetic layer (upper) 43 is facing the left in the Figure (thedirection opposite to Y). Accordingly, the synthesized magnetic momentobtained by adding the magnetic moment of the first pinned magneticlayer (upper) 43 and the magnetic moment of the second pinned magneticlayer (upper) 41 is facing the left in the Figure (the directionopposite to Y). In this way, with the present invention, the synthesizedmagnetic moments formed above and below the free magnetic layer 36 aredirected in mutually opposing directions.

As shown in FIG. 5, with the present invention, the sensing current 114is caused to flow in the direction opposite to X, thereby generating asensing current magnetic field turning to the left as viewed in theFigure.

The synthesized magnetic moment formed below the free magnetic layer 36is facing the right in the Figure (the direction Y), and the synthesizedmagnetic moment formed above the free magnetic layer 36 is facing theleft in the Figure (the direction opposite to Y), so the direction ofthe two synthesized moments match the direction of the sensing currentmagnetic field. Thus, the antiparallel state of the magnetization of thefirst pinned magnetic layer (lower) 32 and the magnetization of thesecond pinned magnetic layer (lower) 34 formed below the free magneticlayer 36, and also the antiparallel state of the magnetization of thefirst pinned magnetic layer (upper) 43 and the magnetization of thesecond pinned magnetic layer (upper) 41 formed above the free magneticlayer 36, can be maintained in a thermally stable state.

If the synthesized magnetic moment formed below the free magnetic layer36 is facing the left, and the synthesized magnetic moment formed abovethe free magnetic layer 36 is facing the right, there is the need tocause the sensing current 114 to flow in the direction X in the Figure,thereby aligning the direction of the sensing current magnetic fieldformed by causing the sensing current to flow, and the synthesizedmagnetic moment.

FIG. 7 and FIG. 9 are embodiments of spin-valve magnetoresistive thinfilm elements wherein the free magnetic layer has been divided into afirst free magnetic layer and a second free magnetic layer with anonmagnetic intermediate layer introduced therebetween. If the firstpinned magnetic layer 52 and second pinned magnetic layer 54 are formedbelow the nonmagnetic electrically conductive layer 55 as with thespin-valve magnetoresistive thin film element shown in FIG. 7, controlof the sensing current should be performed in the same manner as withthe spin-valve magnetoresistive thin film element shown in FIG. 1.

Also, if the first pinned magnetic layer 79 and second pinned magneticlayer 77 are formed above the nonmagnetic electrically conductive layer76 as with the spin-valve magnetoresistive thin film element shown inFIG. 9, control of the sensing current direction should be performed inthe same manner as with the spin-valve magnetoresistive thin filmelement shown in FIG. 3.

As described above, according to the present invention, matching thedirection of the sensing current magnetic field formed by causing thesensing current to flow, and the synthesized magnetic moment obtained byadding the magnetic moment of the first pinned magnetic layer and themagnetic moment of the second pinned magnetic layer. Consequently, theexchange coupling magnetic field (RKKY interaction) acting between thefirst pinned magnetic layer is amplified and the second pinned magneticlayer, and the antiparallel state (Ferri-state) between themagnetization of the first pinned magnetic layer and the magnetizationof the second pinned magnetic layer can be further thermally stabilized.

Particularly, in order to further improve thermal stability, the presentinvention uses a PtMn alloy or the like with a high blocking temperaturefor the antiferromagnetic material comprising the antiferromagneticlayer, and so even if the environment temperature rises greatly incomparison with known arrangements, the antiparallel state (Ferri-state)between the magnetization of the first pinned magnetic layer and themagnetization of the second pinned magnetic layer does not easilycollapse.

Also, if the amount of sensing current is increased to deal with highrecording density, thereby increasing the reproduction output, thesensing current magnetic field also increases accordingly. However, withthe present invention, this sensing current magnetic field acts toamplify the exchange coupling magnetic field acting between the firstpinned magnetic layer and the second pinned magnetic layer, so themagnetization state of the first pinned magnetic layer and the secondpinned magnetic layer is even more stabilized by the increase in thesensing current magnetic field.

This control of the sensing current can be applied in any case using anyantiferromagnetic material for the antiferromagnetic material,regardless of whether or not thermal treatment is necessary forgenerating an exchange coupling magnetic field (exchange anisotropicmagnetic field) at the interface between the antiferromagnetic layer andthe pinned magnetic layer (first pinned magnetic layer), for example.

Further, the magnetization of the pinned magnetic layer can be thermallystabilized even in the case of conventional single spin-valvemagnetoresistive thin film elements wherein the pinned magnetic layer isformed of a single layer, by matching the direction of the sensingcurrent magnetic field generated by causing the sensing current to flowand the direction of magnetization of the pinned magnetic layer.

With the present invention, the relationship between the film thicknessratio of the first pinned magnetic layer and second pinned magneticlayer, the exchange coupling magnetic field (Hex), and ΔMR (rate ofresistance change), was measured, using a spin-valve magnetoresistivethin film element wherein the pinned magnetic layer is divided into afirst pinned magnetic layer and second pinned magnetic layer with anonmagnetic intermediate layer introduced therebetween.

First, the first pinned magnetic layer (the pinned magnetic layer on theside coming into contact with the antiferromagnetic layer) was fixed at20 ängström or 40 ängström, and the film thickness of the second pinnedmagnetic layer was varied, whereby the relationship between thethickness of the second pinned magnetic layer, and the exchange couplingmagnetic field and ΔMR was researched. The film configuration used inthe experiments is from the bottom; the Si substrate/Alumina/Ta(30)/antiferromagnetic layer of PtMn (150)/first pinned magnetic layerof Co (20 or 40)/nonmagnetic intermediate layer of Ru (7)/second pinnedmagnetic layer of Co (X) Cu (25)/nonmagnetic electrically conductivelayer of Cu (25)/free magnetic layer of Co (10)+NiFe (40)/Ta (30). Thenumerals in the parentheses for each layer represent film thickness inunits of ängström.

Also, with the present invention, following completion of the layers ofthe above the spin-valve magnetoresistive thin film element, thespin-valve magnetoresistive thin film element was subjected to thermaltreatment at 260° C. for four hours while applying a magnetic field of200 (Oe), following formation. The results of the experiments are shownin FIGS. 14 and 15.

As shown in FIG. 14, it can be understood that in the event that thethickness tP1 of the first pinned magnetic layer (P1) is fixed at 20ängström, setting the thickness t_(P2) of the second pinned magneticlayer (P2) at 20 ängström results in the exchange coupling magneticfield (Hex) dropping rapidly, and increasing the thickness of thethickness t_(P2) results in the exchange coupling magnetic fielddropping gradually. Also, it can be understood that in the event thatthe thickness t_(P1) of the first pinned magnetic layer (P1) is fixed at40 ängström, setting the thickness t_(P2) of the second pinned magneticlayer (P2) at 40 ängström results in the exchange coupling magneticfield dropping rapidly, and increasing the thickness of the thicknesst_(P2) above 40 ängström results in the exchange coupling magnetic fielddropping gradually. It can also be understood that reducing thethickness of the thickness t_(P2) under 40 ängström results in theexchange coupling magnetic field increasing to 26 ängström, but thatreducing the thickness of the thickness t_(P2) under 26 ängström resultsin the exchange coupling magnetic field dropping.

Now, it is supposed that the reason that the exchange coupling magneticfield drops drastically in the event that the thickness t_(P1) of thefirst pinned magnetic layer (P1) and the thickness t_(P2) of the secondpinned magnetic layer (P2) are the same is because the magnetism of thefirst pinned magnetic layer (P1) and magnetism of the second pinnedmagnetic layer (P2) do not enter an antiparallel state easily, i.e., itis difficult to achieve a so-called Ferri-state.

Now, as shown in the above-described film configuration, the firstpinned magnetic layer (P1) and the second pinned magnetic layer (P2) areboth formed of Co films, and thus have the same saturation magnetization(Ms). Further, due to being set at approximately the same thickness, themagnetic moment (Ms·t_(P1)) of the first pinned magnetic layer (P1) andthe magnetic moment (Ms·t_(P2)) of the second pinned magnetic layer (P2)are set at approximately the same value.

The present invention uses a PtMn alloy for the antiferromagnetic layer,and purports to generate an exchange coupling magnetic field at theinterface between the antiferromagnetic layer and the first pinnedmagnetic layer (P1) by subjecting the formed films to annealing in amagnetic field, thereby pinning the first pinned magnetic layer (P1) ina certain direction.

However, if the magnetic moment of the first pinned magnetic layer (P1)and the second pinned magnetic layer (P2) are approximately the samevalue, both the first pinned magnetic layer (P1) and the second pinnedmagnetic layer (P2) attempt to face the direction of the magnetic fieldat the time of applying the magnetic field and subjecting to thermaltreatment. Originally, an exchange coupling magnetic field (RKKYinteraction) should be generated between the first pinned magnetic layer(P1) and the second pinned magnetic layer (P2), with the magnetizationof the first pinned magnetic layer (P1) and the magnetization of thesecond pinned magnetic layer (P2) being magnetized in an antiparallelstate (Ferri-state). However, here the magnetization of each of thefirst pinned magnetic layer (P1) and the second pinned magnetic layer(P2) both face in the direction of the magnetic field, not easily beingmagnetized in an antiparallel state. Consequently, the magnificationstate of the first pinned magnetic layer (P1) and the second pinnedmagnetic layer (P2) is extremely unstable with regard to externalmagnetic fields or the like.

Accordingly, it is preferable to have a certain amount of differencebetween the magnetic moment of the first pinned magnetic layer (P1) andthe magnetic moment of the second pinned magnetic layer (P2), but asshown in FIG. 14, too great a difference between the film thicknesst_(P1) of the first pinned magnetic layer (P1) and the film thicknesst_(P2) of the second pinned magnetic layer (P2) and too great adifference between the magnetic moment of the first pinned magneticlayer (P1) and the magnetic moment of the second pinned magnetic layer(P2) is a problem since this causes the exchange coupling magnetic fieldto deteriorate, and the antiparallel state easily collapses.

FIGS. 16 and 17 are graphs representing the relationship between thethickness t_(P1) of the first pinned magnetic layer, and the exchangecoupling magnetic field (Hex) and ΔMR, in the event that the thicknesst_(P2) of the second pinned magnetic layer (P2) was fixed at 30ängström, and the film thickness t_(P1) of the first pinned magneticlayer (P1) was varied. The film configuration of the spin-valvemagnetoresistive thin film element used in the experiments is from thebottom; the Si substrate/Alumina/Ta (30) PtMn (150)/first pinnedmagnetic layer of Co (X)/nonmagnetic intermediate layer of Ru (7)/secondpinned magnetic layer of Co (30)/nonmagnetic electrically conductivelayer of Cu (25)/free magnetic layer of Co (10)+NiFe (40)/Ta (30). Thenumerals in the parentheses for each layer represent film thickness inunits of ängström.

Also, with the present invention, upon completion of the layers of theabove spin-valve magnetoresistive thin film element, the spin-valvemagnetoresistive thin film element was subjected to thermal treatment at260° C. for four hours while applying a magnetic field of 200 (Oe).

As shown in FIG. 16, it can be understood that if the thickness t_(P1)of the first pinned magnetic layer (P1) is set at 30 ängström, which isthe same film thickness, as the t_(P2) of the second pinned magneticlayer (P2), the exchange coupling magnetic field (Hex) dropsdrastically. This is due to the above-described reason.

Also, it can also be understood that the exchange coupling magneticfield becomes smaller if the thickness t_(P1) of the first pinnedmagnetic layer (P1) is approximately 32 ängström. This is because themagnetic thickness of the first pinned magnetic layer becomes smallerthan the actual thickness t_(P1) due to a thermal dispersion layer beinggenerated, and approaches the thickness t_(P2) of the second pinnedmagnetic layer (=30 ängström).

This thermal dispersion layer is formed at the interface of theantiferromagnetic layer and the first pinned magnetic layer due to metalelements being dispersed, and as shown in the film configuration usedfor this experiment, the thermal dispersion layer is easily generated ifthe antiferromagnetic layer and pinned magnetic layer are formed belowthe free magnetic layer.

FIG. 18 is a graph representing the relationship between the thicknessof the first pinned magnetic layer and the exchange coupling magneticfield (Hex), in the event that a dual spin-valve magnetoresistive thinfilm element is manufactured, with the two second pinned magnetic layersof the dual spin-valve magnetoresistive thin film element being fixed at20 ängström, and the film thickness of the two first pinned magneticlayers being varied. The film configuration of the spin-valvemagnetoresistive thin film element used in the experiments is from thebottom; the Si substrate Alumina/Ta (30)/antiferromagnetic layer of PtMn(150) first pinned magnetic layer (P1 lower) of Co (X)/nonmagneticintermediate layer of Ru (6)/second pinned magnetic layer (p2 lower) ofCo (20)/nonmagnetic electrically conductive layer of Cu (20)/freemagnetic layer of Co (10)+NiFe (40)+Co (10)/nonmagnetic electricallyconductive layer of Cu (20)/second pinned magnetic layer (12 upper) ofCo (20)/nonmagnetic intermediate layer of Ru (8)/first pinned magneticlayer (P1 upper) of Co (X)/antiferromagnetic layer of PtMn(150)/protecting layer of Ta (30). The numerals in the parentheses foreach layer represent film thickness in units of ängström.

Also, with the present invention, upon completion of the layers of theabove spin-valve magnetoresistive thin film element, the spin-valvemagnetoresistive thin film element was subjected to thermal treatment at260° C. for four hours while applying a magnetic field of 200 (Oe),following formation.

Also, in the experiments, the first pinned magnetic layer (P1 lower)formed below the free magnetic layer was fixed at 25 ängström and thethickness of the first pinned magnetic layer (P1 upper) formed above thefree magnetic layer was changed, and the relationship between thethickness of the first pinned magnetic layer (P1 upper) and the exchangecoupling magnetic field was studied.

Further, the first pinned magnetic layer (P1 upper) formed above thefree magnetic layer was fixed at 25 ängström and the thickness of thefirst pinned magnetic layer (P1 lower) formed below the free magneticlayer was changed, and the relationship between the thickness of thefirst pinned magnetic layer (P1 lower) and the exchange couplingmagnetic field (Hex) was studied.

As shown in FIG. 18, if the first pinned magnetic layer (P1 lower) isfixed at 25 ängström and the thickness of the first pinned magneticlayer (P1 upper) is brought closer to 20 ängström, the exchange couplingmagnetic field gradually grows greater, but at the point that thethickness of the first pinned magnetic layer (P1 upper) reaches around18 to 22 ängström, this thickness is approximately the same as the filmthickness of the first pinned magnetic layer (P1 lower), so the exchangecoupling magnetic field rapidly drops. It can also be understood thatthe exchange coupling magnetic field gradually drops when the thicknessof the first pinned magnetic layer (P1 upper) is gradually increasedfrom 22 ängström to 30 ängström.

Also, as shown in FIG. 18, if the first pinned magnetic layer (P1 upper)is fixed at 25 ängström and the thickness of the first pinned magneticlayer (P1 lower) is brought closer to 20 ängström, the exchange couplingmagnetic field gradually grows greater. However, at the point that thethickness of the first pinned magnetic layer (P1 lower) reaches around18 to 22 ängström, the exchange coupling magnetic field rapidly drops.It can also be understood that the exchange coupling magnetic fieldincreases when the thickness of the first pinned magnetic layer (P1lower) is increased from 22 ängström as far as 26 ängström, but that theexchange coupling magnetic field drops if this is 26 ängström orgreater.

Now, comparing the exchange coupling magnetic field in the first pinnedmagnetic layer (P1) and the exchange coupling magnetic field in thefirst pinned magnetic layer (P1 lower), with the film thickness of thefirst pinned magnetic layer (P1 upper) at around 22 ängström, it can beunderstood that the exchange coupling magnetic field can be made to begreater in an arrangement wherein the film thickness of the first pinnedmagnetic layer (P1 upper) is set at around 22 ängström, as compared toan arrangement wherein the film thickness of the first pinned magneticlayer (P1 lower) is set at around 22 ängström. As described above, thisis due to the fact that a thermal dispersion layer is easily formed atthe interface between the first pinned magnetic layer (P1 lower) and theantiferromagnetic layer, whereby the magnetic thickness of the firstpinned magnetic layer essentially becomes smaller, and becomes about thesame as the thickness of the second pinned magnetic layer (P2 lower).

The (film thickness of the first pinned magnetic layer (P1))/(filmthickness of the second pinned magnetic layer (P2)) whereby an exchangecoupling magnetic field of 500 Oe or greater can be obtained with thepresent invention was studied based on the experiment results shown inFIGS. 14, 16, and 18.

First, as shown in FIG. 14, it can be understood that if the thicknessof the first pinned magnetic layer (P1) is fixed at 20 ängström, the(film thickness of the first pinned magnetic layer (P1))/(film thicknessof the second pinned magnetic layer (P2)) must be set between 0.33 orgreater and 0.91 or smaller, or 1.1 or greater, in order to obtain anexchange coupling magnetic field of 500 (Oe) or greater. The filmthickness of the second pinned magnetic layer (P2) at this time iswithin the range of 10 to 60 ängström (excluding 18 to 22 ängström).

Next, as shown in FIG. 14, it can be understood that if the filmthickness of the first pinned magnetic layer (P1) is fixed at 40ängström, the (film thickness of the first pinned magnetic layer(P1))/(film thickness of the second pinned magnetic layer (P2)) must beset between 0.57 or greater and 0.95 or smaller, or 1.05 or greater and4 or smaller, in order to obtain an exchange coupling magnetic field of500 (Oe) or greater. Incidentally, the film thickness of the secondpinned magnetic layer (P2) at this time is within the range of 10 to 60ängström (excluding 38 to 42 ängström).

Next, as shown in FIG. 16, it can be understood that in the event thatthe film thickness of the second pinned magnetic layer (P2) is fixed at30 ängström, the (film thickness of the first pinned magnetic layer(P1))/(film thickness of the second pinned magnetic layer (P2)) must beset between 0.33 or greater and 0.93 or smaller, or 1.06 or greater and2.33 or smaller, in order to obtain an exchange coupling magnetic fieldof 500 (Oe) or greater. The film thickness of the first pinned magneticlayer (P1) at this time is within the range of 10 to 70 ängström(excluding 28 to 32 ängström).

Further, as shown in FIG. 18, it can be understood that in the case of adual spin-valve magnetoresistive thin film element, an exchange couplingmagnetic field of 500 (Oe) or greater can be obtained as long as therange of 0.9 or greater and 1.1 or smaller is excluded from the range ofthe (film thickness of the first pinned magnetic layer (P1))/(filmthickness of the second pinned magnetic layer (P2)).

Now, the widest range wherein an exchange coupling magnetic field of 500(Oe) or greater can be obtained is between 0.33 or greater and 0.95 orsmaller, or 1.05 or greater and 4 or smaller, for the (film thickness ofthe first pinned magnetic layer (P1))/(film thickness of the secondpinned magnetic layer (P2)).

However, in addition to film thickness ratio, the film thickness of thefirst pinned magnetic layer (P1) and the film thickness of the secondpinned magnetic layer (P2) is also an important factor regarding theexchange coupling magnetic field. Accordingly, with the thickness ratioas described above, and further with the film thickness of the firstpinned magnetic layer (P1) and the film thickness of the second pinnedmagnetic layer (P2) within a range of 10 to 70 ängström, and moreoverwith the absolute value obtained by subtracting the film thickness ofthe second pinned magnetic layer (P2) from the film thickness of thefirst pinned magnetic layer (P1) at 2 ängström or greater, an exchangecoupling magnetic field of 500 (Oe) or greater can be obtained.

Next, the (film thickness of the first pinned magnetic layer (P1))/(filmthickness of the second pinned magnetic layer (P2)) whereby an exchangecoupling magnetic field of 1,000 (Oe) or greater can be obtained withthe present invention was studied.

First, as shown in FIG. 14, in the event that the film thickness of thefirst pinned magnetic layer (P1) is fixed at 20 ängström, setting the(film thickness of the first pinned magnetic layer (P1))/(film thicknessof the second pinned magnetic layer (P2)) between 0.53 and 0.91, or at1.1 or greater, enables an exchange coupling magnetic field of 1,000(Oe) or greater to be obtained. The film thickness of the second pinnedmagnetic layer (P2) at this time is within the range of 10 to 38ängström (excluding 18 to 22 ängström).

Next, as shown in FIG. 14, if the film thickness of the first pinnedmagnetic layer (P1) is fixed at 40 ängström, setting the (film thicknessof the first pinned magnetic layer (P1))/(film thickness of the secondpinned magnetic layer (P2)) between 0.88 and 0.95, or between 1.05 and1.8, enables an exchange coupling magnetic field of 1,000 (Oe) orgreater to be obtained. The film thickness of the second pinned magneticlayer (P2) at this time is within the range of 22 to 45 ängström(excluding 38 to 42 ängström).

Further, as shown in FIG. 16, if the film thickness of the second pinnedmagnetic layer (P2) is fixed at 30 ängström, setting the (film thicknessof the first pinned magnetic layer (P1))/(film thickness of the secondpinned magnetic layer (P2)) between 0.56 and 0.93, or 1.06 and 1.6,enables an exchange coupling magnetic field of 1,000 (Oe) or greater tobe obtained. The film thickness of the first pinned magnetic layer (P1)at this time is within the range of 10 to 50 ängström (excluding 28 to32 ängström).

Also, as shown in FIG. 18, in the case of a dual spin valvemagnetoresistive thin film element, setting the (film thickness of thefirst pinned magnetic layer (P1))/(film thickness of the second pinnedmagnetic layer (P2)) between 0.5 and 0.9, or 1.1 and 1.5, enables anexchange coupling magnetic field of 1,000 (Oe) or greater to beobtained.

Accordingly, in order to obtain an exchange coupling magnetic field of1,000 (Oe) or greater, the (film thickness of the first pinned magneticlayer (P1))/(film thickness of the second pinned magnetic layer (P2))should be set to a range between 0.53 to 0.9 or 1.05 to 1.8, and it isfurther preferable that the film thickness of the first pinned magneticlayer (P1) and second pinned magnetic layer (P2) at this time is withinthe range of 10 to 50 ängström, and even more preferable that theabsolute value obtained by subtracting the film thickness of the secondpinned magnetic layer (P2) from the film thickness of the first pinnedmagnetic layer (P1) is 2 ängström or greater.

Also, as shown in FIG. 15 and FIG. 17, as long as the film thicknessratio and film thickness are within the above ranges, there is littledrop in ΔMR, and a ΔMR of around 6% or higher can be obtained. This ΔMRvalue is either around the same or somewhat lower than the ΔMR of knownspin-valve magnetoresistive thin film elements (speaking only of singlespin-valve magnetoresistive thin film elements).

Also, it can be understood that if the first pinned magnetic layer (P1)is set at 40 ängström, the ΔMR is somewhat smaller than if the firstpinned magnetic layer (P1) is set at 20 ängström.

The first pinned magnetic layer (P1) is actually a layer which does nothave bearing on the ΔMR, and this ΔMR is determined by the relationshipbetween the pinned magnetism of the second pinned magnetic layer (P2)and the fluctuating magnetization of the free magnetic layer. However,the sensing current also flows to the first pinned magnetic layer (P1)which does not have bearing on the ΔMR, thus generating a so-calledshunt loss (diversion loss), and this shunt loss increases as the filmthickness of the first pinned magnetic layer (P1) increases. Due to theabove reasons, ΔMR tends to drop as the film thickness of the firstpinned magnetic layer (P1) increases.

Next, measurement was made regarding the appropriate thickness of thenonmagnetic intermediate layer formed between the first pinned magneticlayer (P1) and the second pinned magnetic layer (P2). For thisexperiment, two types of spin-valve magnetoresistive thin film elementswere manufactured: a bottom type wherein the antiferromagnetic layer isformed below the free magnetic layer, and a top type wherein theantiferromagnetic layer is formed above the free magnetic layer. Therelationship between the thickness of the nonmagnetic intermediate layerand the exchange coupling magnetic field was then studied for these. Thefilm configuration of the bottom type spin-valve magnetoresistive thinfilm element used in the experiment is from the bottom; the Si substrateAlumina Ta (30)/antiferromagnetic layer of PtMn (200)/first pinnedmagnetic layer of Co (20)/nonmagnetic intermediate layer of Ru(X)/second pinned magnetic layer of Co (25)/ nonmagnetic electricallyconductive layer of Co (10)/free magnetic layer of Co (10)+NiFe (40)/Ta(30).

The film configuration of the top type spin-valve magnetoresistive thinfilm element used in the experiment is from the bottom; the Sisubstrate/Alumina/Ta (30)/free magnetic layer of NiFe (40)+Co(10)/nonmagnetic electrically conductive layer of Cu (25)/second pinnedmagnetic layer of Co (25)/nonmagnetic intermediate layer of Ru (X)/firstpinned magnetic layer of Co (20)/antiferromagnetic layer of PtMn(200)/Ta (30). The numerals in the parentheses for each layer representfilm thickness in units of ängström.

Also, with the present invention, upon completion of the layers of theabove spin-valve magnetoresistive thin film element, the spin-valvemagnetoresistive thin film element was subjected to thermal treatment at260° C. for four hours while applying a magnetic field of 200 (Oe),following formation. The experiment results are shown in FIG. 19.

As can be seen in FIG. 19, the behavior of the exchange couplingmagnetic field in regard to the thickness of the Ru layer (thenonmagnetic intermediate layer) changes greatly between the top type andthe bottom type.

Since the present invention holds that a range wherein an exchangecoupling magnetic field of 500 (Oe) or greater can be obtained ispreferable, it can be understood that the thickness range of the Rulayer in the top type spin-valve magnetoresistive thin film elementwherein an exchange coupling magnetic field of 500 (Oe) or greater canbe obtained is from 2.5 to 6.2 ängström or 6.6 to 10.7 Ångstrom. Furtherpreferable is a range wherein an exchange coupling magnetic field of1,000 (Oe) or greater can be obtained, and it can be understood that thethickness range of the Ru layer wherein an exchange coupling magneticfield of 1,000 (Oe) or greater can be obtained is from 2.8 to 6.2ängström or 6.8 to 10.3 ängström.

Next, with the bottom type spin-valve magnetoresistive thin filmelement, it can be understood that the thickness range of the Ru layerwherein an exchange coupling magnetic field of 500 (Oe) or greater canbe obtained is from 3.6 to 9.6 ängström. Further, a range for the Rulayer of 4.0 to 9.4 ängström will yield an exchange coupling magneticfield of 1,000 (Oe) or greater.

It is supposed that the reason why the appropriate thickness range forthe nonmagnetic intermediate layer differs between the case of a toptype spin-valve magnetoresistive thin film element and a bottom typespin valve magnetoresistive thin film element, is that the exchangecoupling magnetic field (RKKY interaction) acting between the firstpinned magnetic layer and the second pinned magnetic layer reacts to therelationship with the lattice constants of the base layer or the energyband value of conduction electrons at the magnetic layers, in anextremely sensitive manner.

Next, with the present invention, four types of spin valvemagnetoresistive thin film elements (single spin-valve magnetoresistivethin film elements) were manufactured, and the relationship between thethickness of the antiferromagnetic layer (PtMn alloy) of each spin-valvemagnetoresistive thin film element and the exchange coupling magneticfield was measured.

The first and second embodiments are spin-valve magnetoresistive thinfilm elements wherein the pinned magnetic layer is divided into the twolayers of the first pinned magnetic layer and the second pinned magneticlayer, with a nonmagnetic intermediate layer introduced therebetween,and the first and second comparative examples are known spin-valvemagnetoresistive thin film element wherein the pinned magnetic layer isformed of a single layer.

First, the spin-valve magnetoresistive thin film element according tothe first embodiment is a top type wherein the antiferromagnetic layeris formed above the free magnetic layer. The film configuration is fromthe bottom; the Si substrate Alumina/Ta (30)/free magnetic layer of NiFe(40)+Co (10)/nonmagnetic electrically conductive layer of Cu (25)/secondpinned magnetic layer of Co (25)/nonmagnetic intermediate layer of Ru(4)/first pinned magnetic layer of Co (20)/antiferromagnetic layer ofPtMn (X)/Ta (30).

The spin-valve magnetoresistive thin film element according to thesecond embodiment is a bottom type wherein the antiferromagnetic layeris formed below the free magnetic layer. The film configuration is fromthe bottom; the Si substrate/Alumina/Ta (30)/antiferromagnetic layer ofPtMn (X)/first pinned magnetic layer of Co (20)/nonmagnetic intermediatelayer of Ru (8)/second pinned magnetic layer of Co (25)/nonmagneticelectrically conductive layer of Cu (25)/free magnetic layer of Co(10)+NiFe (40)/Ta (30).

Also, the spin-valve magnetoresistive thin film element according to thefirst comparative example is a top type wherein the antiferromagneticlayer is formed above the free magnetic layer. The film configuration isfrom the bottom; the Si substrate/Alumina/Ta (30)/free magnetic layer ofNiFe (40)+Co (10)/nonmagnetic electrically conductive layer of Cu(25)/pinned magnetic layer of Co (40)/antiferromagnetic layer of PtMn(X)/Ta (30).

The spin-valve magnetoresistive thin film element according to thesecond comparative example is a bottom type wherein theantiferromagnetic layer is formed below the free magnetic layer. Thefilm configuration is from the bottom; the Si substrate/Alumina/Ta(30)/antiferromagnetic layer of PtMn (X) |pinned magnetic layer of Co(40)/nonmagnetic electrically conductive layer of Cu (25)/free magneticlayer of Co (10)+NiFe (40)/Ta (30).

The numerals in the parentheses for each layer represent film thicknessin units of ängström, for the film structure of each spin-valvemagnetoresistive thin film element.

Also, with the present invention, the spin-valve magnetoresistive thinfilm elements according to the first and second embodiments weresubjected to thermal treatment at 260° C. for four hours while applyinga magnetic field of 200 (Oe), following formation. The spin-valvemagnetoresistive thin film elements according to the first and secondcomparative examples were subjected to the same, only while applying amagnetic field of 2 k(Oe).

As shown in FIG. 20, the exchange coupling magnetic field can beincreased with each of the four types of spin valve magnetoresistivethin film elements by increasing the thickness of the PtMn alloy.

Now, since the present invention holds that a range wherein an exchangecoupling magnetic field of 500 (Oe) or greater can be obtained is apreferable range, it can be understood that both the first and secondcomparative examples require the PtMn alloy to be formed to a thicknessof at least 200 ängström; otherwise, an exchange coupling magnetic fieldof 500 (Oe) or greater cannot be obtained.

On the other hand, it can be understood that the first and secondembodiments can obtain an exchange coupling magnetic field of 500 (Oe)or greater by the PtMn alloy being formed to a thickness of at 90ängström or more. Accordingly, with the present invention, thepreferable range for the thickness of the PtMn alloy is set within therange of 90 to 200 ängström.

Further, as can be seen in FIG. 20, the first and second embodiments canobtain an exchange coupling magnetic field of 1,000 (Oe) or greater bythe PtMn alloy being formed to a thickness of at 100 ängström or more.Accordingly, with the present invention, an even more preferable rangefor the thickness of the PtMn alloy is set within the range of 100 to200 ängström.

Next, with the present invention, two types of dual spin-valvemagnetoresistive thin film elements were manufactured, and therelationship between the thickness of the antiferromagnetic layer (PtMnalloy) of each spin-valve magnetoresistive thin film element and theexchange coupling magnetic field was measured.

The present invention is a dual spin-valve magnetoresistive thin filmelement wherein the pinned magnetic layers are divided into the twolayers of the first pinned magnetic layer and the second pinned magneticlayer, with a nonmagnetic intermediate layer introduced therebetween,and the comparative example is a known dual spin-valve magnetoresistivethin film element wherein the pinned magnetic layers are formed of asingle layer.

The film configuration of the spin-valve magnetoresistive thin filmelement according to the embodiment is from the bottom; the Sisubstrate/Alumina/Ta (30)/antiferromagnetic layer of PtMn (X)/firstpinned magnetic layer of Co (20)/nonmagnetic intermediate layer of Ru(6)/second pinned magnetic layer of Co (25)/nonmagnetic electricallyconductive layer of Cu (20)/free magnetic layer of Co (10)+NiFe (40)+Co(10)/nonmagnetic electrically conductive layer of Cu (20)/second pinnedmagnetic layer of Co (20)/nonmagnetic intermediate layer of Ru (8)/firstpinned magnetic layer of Co (25)/antiferromagnetic layer of PtMn (X)/Ta(30).

The film configuration of the spin-valve magnetoresistive thin filmelement according to the comparative example is from the bottom; the Sisubstrate/Alumina/Ta (30)/antiferromagnetic layer of PtMn (X)/pinnedmagnetic layer of Co (30)/nonmagnetic electrically conductive layer ofCu (20)/free magnetic layer of Co (10)+NiFe (40)+Co (10)/nonmagneticelectrically conductive layer of Cu (20)/pinned magnetic layer of Co(30)/antiferromagnetic layer of PtMn (X)/Ta (30).

The numerals in the parentheses for each layer represent film thicknessin units of ängström, for the film structures of each spin-valvemagnetoresistive thin film element.

Also, following completion of the layers of the spin valvemagnetoresistive thin film element, the embodiment was subjected tothermal treatment at 260° C. for four hours while applying a magneticfield of 200 (Oe), and the comparative example was subjected to the samewhile applying a magnetic field of 2 k(Oe). The experiment results areshown in FIG. 21.

As shown in FIG. 21, it can be understood that the comparative examplerequires the PtMn alloy to be formed to a thickness of at least 200ängström; otherwise, an exchange coupling magnetic field of 500 (Oe) orgreater cannot be obtained.

On the other hand, it can be understood that the embodiment can obtainan exchange coupling magnetic field of 500 (Oe) or greater by the PtMnalloy being formed to a thickness of at 100 ängström or more.Accordingly, with the present invention, the preferable range for thethickness of the antiferromagnetic layer is set within the range of 100to 200 ängström. Further, the embodiment can obtain an exchange couplingmagnetic field of 1,000 (Oe) or greater by the PtMn alloy being formedto a thickness of at 110 ängström or more. Accordingly, with the presentinvention, an even more preferable range for the thickness of theantiferromagnetic layer is set within the range of 110 to 200 ängström.

FIG. 22 is a graph showing the relationship between the film thicknessof the PtMn alloy and the ΔMR. As shown in FIG. 22, with the comparativeexample, forming the thickness of the PtMn alloy at 200 ängström or moreenables ΔMR of around 10% or more to be obtained. However, with theembodiment, ΔMR around that of known arrangements can be secured eventhough the thickness of the PtMn alloy is reduced to around 100ängström.

Now, of the layered films making up the spin-valve magnetoresistive thinfilm element, the thickest is the antiferromagnetic layer. Thus,according to the present invention, even in the event that the thicknessof the antiferromagnetic layer is reduced as shown in FIGS. 20 and 21,specifically, forming the antiferromagnetic layer at less than half thethickness of known spin-valve magnetoresistive thin film elements, alarge exchange coupling magnetic field can be obtained. Hence, accordingto the present invention, the thickness of the overall spin-valvemagnetoresistive thin film element can be reduced, and as shown in FIG.13, the gap length G1 can be reduced even in the event that the gaplayer 121 and gap layer 125 formed above and below the spin-valvemagnetoresistive thin film element 122 are made to be thick enough tomaintain sufficient insulation, thereby realizing a narrow gap.

Next, a spin-valve magnetoresistive thin film element according to thepresent invention wherein the free magnetic layer is divided into afirst free magnetic layer and second free magnetic layer with anonmagnetic intermediate layer introduced therebetween was manufactured,and the relationship between the thickness ratio of the first freemagnetic layer and second free magnetic layer, and the exchange couplingmagnetic field was measured. First, the film thickness of the first freemagnetic layer (the free magnetic layer at the side which comes intocontact with the nonmagnetic electrically conductive layer, and directlycontributes to the ΔMR) was fixed at 50 ängström, and the film thicknessof the second free magnetic layer (the free magnetic layer at the sidewhich does not directly contribute to the ΔMR) was variable.

The film configuration is from the bottom; the Si substrate/Alumina/Ta(30)/second free magnetic layer (F2) of NiFe (X)/nonmagneticintermediate layer of Ru (8)/first free magnetic layer (F1) of NiFe(40)+Co (10)/nonmagnetic electrically conductive layer of Cu (20)/Ru(8)/antiferromagnetic layer of PtMn (150)/Ta (30). The numerals in theparentheses for each layer represent film thickness in units ofängström.

The spin-valve magnetoresistive thin film element was subjected tothermal treatment at 260° C. for four hours while applying a magneticfield of 200 (Oe), following formation.

As shown in FIG. 23, it can be understood that in the event that thethickness of the second free magnetic layer (F2) increases to around 40ängström, the exchange coupling magnetic field increases. It can also beunderstood that in the event that the thickness of the second freemagnetic layer (F2) increases to around 60 Ångström and above, theexchange coupling magnetic field gradually decreases.

The exchange coupling magnetic field rapidly became small to the pointof being not measurable while the thickness of the second free magneticlayer (F2) was in the range between 40 to 60 ängström. The reason isthat the thickness of the first free magnetic layer (F1) (=50 ängström)and the thickness of the second free magnetic layer become approximatelythe same value, so the magnetic moments of the first free magnetic layer(F1) and the second free magnetic layer (F2) are approximately the same,and both the magnetization of the first free magnetic layer (F1) and themagnetization of the second free magnetic layer (F2) attempt to face inthe same direction, which is the direction of applying the magneticfield. If the magnetic moments are different, an exchange couplingmagnetic field (RKKY interaction) is generated between the first freemagnetic layer (F1) and the second free magnetic layer (F2), so themagnetization of the first free magnetic layer (F1) and themagnetization of the second free magnetic layer (F2) attempt to assumean antiparallel state, but here, as described above, the magnetizationof both the first free magnetic layer (F1) and the second free magneticlayer (F2) attempt to face in the same direction, so the magnetizationstate between the first free magnetic layer (F1) and the second freemagnetic layer (F2) becomes unstable, and as described later, therelative angle between the fluctuating magnetization of the second freemagnetic layer (F2) and the pinned magnetization of the pinned magneticlayer (first pinned magnetic layer) cannot be controlled, and ΔMR dropsrapidly.

Now, since the present invention holds that a range wherein an exchangecoupling magnetic field of 500 (Oe) or greater can be obtained is apreferable range, it can be understood that, as shown in FIG. 23,forming the (thickness of the first free magnetic layer (F1))/(thicknessof the second free magnetic layer (F2)) within a range of 0.56 to 0.83or 1.25 to 5 allows an exchange coupling magnetic field of 500 (Oe) orgreater to be obtained.

Further preferable is forming the (thickness of the first free magneticlayer (F1)/thickness of the second free magnetic layer (F2)) within arange of 0.61 to 0.83 or 1.25 to 2.1, as an exchange coupling magneticfield of 1,000 (Oe) or greater can be obtained.

Next, a spin-valve magnetoresistive thin film element according to thepresent invention wherein the free magnetic layer is divided into afirst free magnetic layer and second free magnetic layer with anonmagnetic intermediate layer introduced therebetween was manufactured,and the relationship between the thickness ratio of the first freemagnetic layer and second free magnetic layer, and the ΔMR was measured.First, the film thickness of the second free magnetic layer (the freemagnetic layer at the side which does not directly contribute to theΔMR) was fixed at 20 ängström, and the film thickness of the first freemagnetic layer (the free magnetic layer at the side which comes intocontact with the nonmagnetic electrically conductive layer, and directlycontributes to the ΔMR) was variable.

The film configuration is from the bottom; the Si substrate/Alumina/Ta(30)/second free magnetic layer of NiFe (20)/nonmagnetic intermediatelayer of Ru (8)/first free magnetic layer of NiFe (X)+Co(10)/nonmagnetic electrically conductive layer of Cu (20)/first pinnedmagnetic layer of Co (25)/nonmagnetic intermediate layer of Ru(8)/second pinned magnetic layer of Co (20)/antiferromagnetic layer ofPtMn (15)/Ta (30). The numerals in the parentheses for each layerrepresent film thickness in units of ängström.

Now, with the present invention, the spin-valve magnetoresistive thinfilm element was subjected to thermal treatment at 260° C. for fourhours while applying a magnetic field of 200 (Oe), following formation.Also, as can be understood from the above film configuration, the firstfree magnetic layer in the present invention is formed of two layers,and the thickness of the NiFe film is changed. The results of theexperiment are shown in FIG. 24, wherein the horizontal axis is thetotal thickness of the first free magnetic layer obtained by adding thethickness of the NiFe alloy and the thickness of the Co film (=10ängström).

As shown in FIG. 24, it can be understood that as the thickness of thefirst free magnetic layer (F1) approaches 20 ängström, the thicknessbecomes approximately the same as that of the second free magnetic layer(F2), so the ΔMR drops rapidly. Also, as shown in FIG. 24, if that thethickness of the first free magnetic layer (F1) reaches around 30ängström or more, the ΔMR increases, and ΔMR around that of knownspin-valve magnetoresistive thin film elements (single spin-valvemagnetoresistive thin film elements) can be obtained.

Now, as shown in FIG. 24, the range of the (thickness of the first freemagnetic layer (F1)/(thickness of the second free magnetic layer (F2))wherein an exchange coupling magnetic field of 500 (Oe) or greater canbe obtained as yielded by FIG. 23, and high ΔMR can be obtained bysetting the range of the (thickness of the first free magnetic layer(F1)/thickness of the second free magnetic layer (F2)) within the rangeof 1.25 to 5.

Next, in the present invention, the thickness of the nonmagneticintermediate layer introduced between the first free magnetic layer andsecond free magnetic layer was changed, and the relationship between thethickness of the nonmagnetic intermediate layer and the exchangecoupling magnetic field was measured.

The film configuration for the spin-valve magnetoresistive thin filmelement (dual spin-valve magnetoresistive thin film element) used in theexperiment is from the bottom; the Si substrate/Alumina/Ta(30)/antiferromagnetic layer of PtMn (150)/Ru (6)/nonmagneticelectrically conductive layer of Cu (20)/first free magnetic layer of Co(10)+NiFe (50)/nonmagnetic intermediate layer of Ru (X)/first freemagnetic layer of NiFe (30)+Co (10)/nonmagnetic electrically conductivelayer of Cu (20)/Ru (8)/antiferromagnetic layer of PtMn (150)/Ta (30).The numerals in the parentheses for each layer represent film thicknessin units of ängström.

Also, with the present invention, the spin-valve magnetoresistive thinfilm element was subjected to thermal treatment at 260° C. for fourhours while applying a magnetic field of 200 (Oe), following formation.The experiment results are shown in FIG. 20.

As shown in FIG. 20, it can be understood that the Ru film should beformed to a thickness within a range of 5.5 to 10.0 ängström in order toobtain an exchange coupling magnetic field of 500 (Oe) or greater. Itcan also be understood that the Ru film should be formed to a thicknesswithin a range of 5.9 to 9.4 ängström in order to obtain an exchangecoupling magnetic field of 1,000 (Oe) or greater.

According to the present invention as described above, the magnetizationstate of the pinned magnetic layer can be maintained in an extremelystable state, by dividing the pinned magnetic layer into a first pinnedmagnetic layer and second pinned magnetic layer with a nonmagneticintermediate layer introduced therebetween, and placing themagnetization of the first pinned magnetic layer and the magnetizationof the second pinned magnetic layer in an antiparallel state by means ofthe exchange coupling magnetic field (RKKY interaction) generatedbetween the first pinned magnetic layer and second pinned magneticlayer.

Particularly, with the present invention, an exchange coupling magneticfield of 500 (Oe) or greater, or even more preferably of 1,000 (Oe) orgreater can be obtained by appropriately adjusting the thickness ratiobetween the first pinned magnetic layer and second pinned magneticlayer, and the film thickness thereof.

Also, with the present invention, the nonmagnetic intermediate layerintroduced between the first pinned magnetic layer and second pinnedmagnetic layer is formed of Ru, Rh, Ir, Cr, Re, Cu, or the like, andfurther, the thickness of the nonmagnetic intermediate layer is adjustedto an appropriate level for both the case wherein the nonmagneticintermediate layer is formed above the free magnetic layer and the casewherein the nonmagnetic intermediate layer is formed below the freemagnetic layer, thereby obtaining an exchange coupling magnetic field of500 (Oe) or greater, or even more preferably of 1,000 (Oe) or greater.

Further, with the present invention, a PtMn alloy is used as theantiferromagnetic layer, since PtMn alloys have high blockingtemperature, the exchange coupling magnetic field (exchange anisotropicmagnetic field) generated at the interface between the antiferromagneticlayer and the pinned magnetic layer (first pinned magnetic layer) isgreat, and the corrosion-resistant properties thereof are excellent, asan antiferromagnetic material. Alternatively, X—Mn alloys (wherein X isone or a plurality of the following elements: Pd, Ir, Rh, Ru, Os) orPtMn—X′ alloys (wherein X′ is one or a plurality of the followingelements: Pd, Ir, Rh, Ru, Os, Au, Ag) may be used.

In an arrangement such as with the present invention wherein the pinnedmagnetic layer has been divided into the two layers of the first pinnedmagnetic layer and second pinned magnetic layer, an exchange couplingmagnetic field of 500 (Oe) or greater, or even more preferably of 1,000(Oe) or greater can be obtained, even if the thickness of theantiferromagnetic layer is around half as thick as known arrangements.

Further, with the present invention, it is preferable that, as with thepinned magnetic layer, the free magnetic layer be divided and formed ofa first free magnetic layer and second free magnetic layer, with anonmagnetic intermediate layer introduced therebetween. An exchangecoupling magnetic field (RKKY interaction) is generated between thefirst free magnetic layer and second free magnetic layer, and themagnetization of the first free magnetic layer and the magnetization ofthe second free magnetic layer are magnetized in an antiparallel manner,so as to be inverted with good sensitivity to external magnetic fields.

Also, with the present invention, forming the film thickness ratio ofthe first free magnetic layer and the second free magnetic layer at anappropriate range, and also forming the nonmagnetic intermediate layerintroduced between the first free magnetic layer and the second freemagnetic layer of an Ru film or the like, and further forming thethickness of the nonmagnetic intermediate layer within an appropriaterange, enables an exchange coupling magnetic field of 500 (Oe) orgreater to be obtained, and more preferably, an exchange couplingmagnetic field of 1,000 (Oe) or greater to be obtained.

Further, according to the present invention, in the event of using anantiferromagnetic layer which requires thermal treatment at theinterface with the first pinned magnetic layer, appropriately adjustingthe magnitude of the magnetic moment of the first pinned magnetic layerand the magnetic moment of the second pinned magnetic layer, and alsoappropriately adjusting the magnitude and direction of the magneticfield to be applied during thermal treatment, allows the magnetizationof the first pinned magnetic layer to be directed in the desireddirection, and further enables appropriate control of the magnetizationof the first pinned magnetic layer and the magnetization of the secondpinned magnetic layer in an antiparallel manner.

Further, according to the present invention, matching the direction ofthe sensing current magnetic field generated by causing the sensingcurrent to flow, and the direction of the synthesized magnetic momentobtained by adding the magnetic moment of the first pinned magneticlayer and the magnetic moment of the second pinned magnetic layer,enables the magnetization state of the first pinned magnetic layer andsecond pinned magnetic layer to be even more thermally stable.

This control of the sensing current direction can be applied in any caseusing any antiferromagnetic material for the antiferromagnetic layer,regardless of whether or not thermal treatment is necessary forgenerating an exchange coupling magnetic field (exchange anisotropicmagnetic field) at the interface between the antiferromagnetic layer andthe pinned magnetic layer (first pinned magnetic layer), for example.

Further, the magnetization of the pinned magnetic layer can be thermallystabilized even in the case of known single spin-valve magnetoresistivethin film elements wherein the pinned magnetic layer is formed of asingle layer, by matching the direction of the sensing current magneticfield generated by causing the sensing current to flow, and thedirection of magnetization of the pinned magnetic layer.

Also, according to the second aspect of the present invention, themagnetization state of the pinned magnetic layer can be maintained in anextremely stable state, by dividing the pinned magnetic layer into afirst pinned magnetic layer and second pinned magnetic layer with anonmagnetic intermediate layer introduced therebetween, and placing themagnetization of the first pinned magnetic layer and the magnetizationof the second pinned magnetic layer in an antiparallel state by means ofthe exchange coupling magnetic field (RKKY interaction) generatedbetween the first pinned magnetic layer and second pinned magneticlayer.

Further, with the present invention, matching the direction of thesensing current magnetic field generated by causing the sensing currentto flow, and the direction of the synthesized magnetic moment obtainedby adding the magnetic moment of the first pinned magnetic layer and themagnetic moment of the second pinned magnetic layer, enables themagnetization state of the first pinned magnetic layer and second pinnedmagnetic layer to be even more thermally stable.

This control of the sensing current direction can be applied in any caseusing any antiferromagnetic material for the antiferromagnetic layer,regardless of whether or not thermal treatment is necessary forgenerating an exchange coupling magnetic field (exchange anisotropicmagnetic field) at the interface between the antiferromagnetic layer andthe pinned magnetic layer (first pinned magnetic layer), for example.

Further, the magnetization of the pinned magnetic layer can be thermallystabilized even in the case of known single spin-valve magnetoresistivethin film elements wherein the pinned magnetic layer is formed of asingle layer, by matching the direction of the sensing current magneticfield generated by causing the sensing current to flow, and thedirection of magnetization of the pinned magnetic layer.

Also, with the present invention, adjusting the film thickness ratio andthe thickness of the first pinned magnetic layer and the second pinnedmagnetic layer within appropriate ranges enables an exchange couplingmagnetic field of 500 (Oe) or greater to be obtained, and morepreferably, an exchange coupling magnetic field of 1,000 (Oe) or greaterto be obtained.

Also, with the present invention, the nonmagnetic intermediate layerintroduced between the first pinned magnetic layer and second pinnedmagnetic layer is formed of Ru, Rh, Ir, Cr, Re, Cu, or the like, andfurther, the thickness of the nonmagnetic intermediate layer is adjustedto an appropriate level for both the case wherein the nonmagneticintermediate layer is formed above the free magnetic layer and the casewherein the nonmagnetic intermediate layer is formed below the freemagnetic layer, thereby obtaining an exchange coupling magnetic field of500 (Oe) or greater, or even more preferably of 1,000 (Oe) or greater.

Further, with the present invention, a PtMn alloy is used as theantiferromagnetic layer, since PtMn alloys have high blockingtemperature, the exchange coupling magnetic field (exchange anisotropicmagnetic field) generated at the interface between the antiferromagneticlayer and the pinned magnetic layer (first pinned magnetic layer) isgreat, and the corrosion-resistant properties thereof are excellent, asan antiferromagnetic material. Alternatively, X—Mn alloys (wherein X isone or a plurality of the following elements: Pd, Ir, Rh, Ru, Os) orPtMn—X′ alloys (wherein X′ is one or a plurality of the followingelements: Pd, Ir, Rh, Ru, Os, Au, Ag) may be used.

In an arrangement such as with the present invention wherein the pinnedmagnetic layer has been divided into the two layers of the first pinnedmagnetic layer and second pinned magnetic layer, an exchange couplingmagnetic field of 500 (Oe) or greater, or even more preferably of 1,000(Oe) or greater can be obtained, even if the thickness of theantiferromagnetic layer is around half as thick as known arrangements.

Further, with the present invention, it is preferable that, as with thepinned magnetic layer, the free magnetic layer be divided and formed ofa first free magnetic layer and second free magnetic layer, with anonmagnetic intermediate layer introduced therebetween. An exchangecoupling magnetic field (RKKY interaction) is generated between thefirst free magnetic layer and second free magnetic layer, and themagnetization of the first free magnetic layer and the magnetization ofthe second free magnetic layer are magnetized in an antiparallel manner,so as to be inverted with good sensitivity to external magnetic fields.

Also, with the present invention, forming the film thickness ratio ofthe first free magnetic layer and the second free magnetic layer withinan appropriate range, forming the nonmagnetic intermediate layerintroduced between the first free magnetic layer and the second freemagnetic layer of an Ru film or the like, and further forming thethickness of the nonmagnetic intermediate layer within an appropriaterange, enables an exchange coupling magnetic field of 500 (Oe) orgreater to be obtained, and more preferably, an exchange couplingmagnetic field of 1,000 (Oe) or greater to be obtained.

Further, according to the present invention, in the event of using anantiferromagnetic layer which requires thermal treatment at theinterface with the first pinned magnetic layer, appropriately adjustingthe magnitude of the magnetic moment of the first pinned magnetic layerand the magnetic moment of the second pinned magnetic layer, and alsoappropriately adjusting the magnitude and direction of the magneticfield to be applied during thermal treatment, allows the magnetizationof the first pinned magnetic layer to be directed in the desireddirection, and further enables appropriate control of the magnetizationof the first pinned magnetic layer and the magnetization of the secondpinned magnetic layer in an antiparallel manner.

Also, according to the third aspect of the present invention, themagnetization state of the pinned magnetic layer can be maintained in anextremely stable state, by dividing the pinned magnetic layer into afirst pinned magnetic layer and second pinned magnetic layer with anonmagnetic intermediate layer introduced therebetween, and placing themagnetization of the first pinned magnetic layer and the magnetizationof the second pinned magnetic layer in an antiparallel state by means ofthe exchange coupling magnetic field (RKKY interaction) generatedbetween the first pinned magnetic layer and second pinned magneticlayer.

Particularly, with the present invention, in the event of using anantiferromagnetic layer which requires thermal treatment at theinterface with the first pinned magnetic layer, appropriately adjustingthe magnitude of the magnetic moment of the first pinned magnetic layerand the magnetic moment of the second pinned magnetic layer, and alsoappropriately adjusting the magnitude and direction of the magneticfield to be applied during thermal treatment, enables appropriatecontrol of the magnetization of the first free magnetic layer and themagnetization of the second free magnetic layer in an antiparallelmanner, and further allows the magnetization of the first pinnedmagnetic layer and the magnetization of the second pinned magnetic layerto be directed in the desired direction.

Further, with the present invention, a PtMn alloy is given as anantiferromagnetic layer used for the antiferromagnetic layer whichrequires thermal treatment in order to generate an exchange couplingmagnetic field (exchange anisotropic magnetic field) at the interfacebetween the antiferromagnetic layer and the first pinned magnetic layer,since PtMn alloys have high blocking temperature, the exchange couplingmagnetic field (exchange anisotropic magnetic field) generated at theinterface between the antiferromagnetic layer and the pinned magneticlayer (first pinned magnetic layer) is great, and thecorrosion-resistant properties thereof are excellent. Also, with thepresent invention, X—Mn alloys (wherein X is one or a plurality of thefollowing elements: Pd, Ir, Rh, Ru, Os) or PtMn—X′ alloys (wherein X′ isone or a plurality of the following elements: Pd, Ir, Rh, Ru, Os, Au,Ag) may be used instead of PtMn alloys.

Also, with the present invention, adjusting the film thickness ratio andthe thickness of the first pinned magnetic layer and the second pinnedmagnetic layer within appropriate ranges enables an exchange couplingmagnetic field of 500 (Oe) or greater to be obtained, and morepreferably, an exchange coupling magnetic field of 1,000 (Oe) or greaterto be obtained.

Also, with the present invention, the nonmagnetic intermediate layerintroduced between the first pinned magnetic layer and second pinnedmagnetic layer is formed of Ru, Rh, Ir, Cr, Re, Cu, or the like, andfurther, the thickness of the nonmagnetic intermediate layer is adjustedto an appropriate level for both the case wherein the nonmagneticintermediate layer is formed above the free magnetic layer and the casewherein the nonmagnetic intermediate layer is formed below the freemagnetic layer, thereby obtaining an exchange coupling magnetic field of500 (Oe) or greater, or even more preferably of 1,000 (Oe) or greater.

In an arrangement such as with the present invention wherein the pinnedmagnetic layer has been divided into the two layers of the first pinnedmagnetic layer and second pinned magnetic layer, an exchange couplingmagnetic field of 500 (Oe) or greater, or even more preferably of 1,000(Oe) or greater can be obtained, even if the thickness of theantiferromagnetic layer is around half as thick as known arrangements.

Further, with the present invention, it is preferable that, as with thepinned magnetic layer, the free magnetic layer be divided and formed ofa first free magnetic layer and second free magnetic layer, with anonmagnetic intermediate layer introduced therebetween. An exchangecoupling magnetic field (RKKY interaction) is generated between thefirst free magnetic layer and second free magnetic layer, and themagnetization of the first free magnetic layer and the magnetization ofthe second free magnetic layer are magnetized in an antiparallel manner,so as to be inverted with good sensitivity to external magnetic fields.

Also, with the present invention, forming the film thickness ratio ofthe first free magnetic layer and the second free magnetic layer at anappropriate range, forming the nonmagnetic intermediate layer introducedbetween the first free magnetic layer and the second free magnetic layerof an Ru film or the like, and further forming the thickness of thenonmagnetic intermediate layer within an appropriate range, enables anexchange coupling magnetic field of 500 (Oe) or greater to be obtained,and more preferably, an exchange coupling magnetic field of 1,000 (Oe)or greater to be obtained.

Further, with the present invention, matching the direction of thesensing current magnetic field generated by causing the sensing currentto flow, and the direction of the synthesized magnetic moment obtainedby adding the magnetic moment of the first pinned magnetic layer and themagnetic moment of the second pinned magnetic layer, enables themagnetization state of the first pinned magnetic layer and second pinnedmagnetic layer to be even more thermally stable.

This control of the sensing current can be applied in any case using anyantiferromagnetic material for the antiferromagnetic layer, regardlessof whether or not thermal treatment is necessary for generating anexchange coupling magnetic field (exchange anisotropic magnetic field)at the interface between the antiferromagnetic layer and the pinnedmagnetic layer (first pinned magnetic layer), for example.

Further, the magnetization of the pinned magnetic layer can be thermallystabilized even in the case of single spin-valve magnetoresistive thinfilm elements wherein the pinned magnetic layer is formed of a singlelayer, by matching the direction of the sensing current magnetic fieldgenerated by causing the sensing current to flow, and the direction ofmagnetization of the pinned magnetic layer.

What is claimed is:
 1. A spin-valve magnetoresistive thin film element configured to read a magnetic recording medium, said thin film element comprising: an antiferromagnetic layer, wherein said antiferromagnetic layer comprises one of an X—Mn alloy, where X is selected from the group consisting of Pt, Pd, Ir, Rh, Ru, Os and combinations thereof, and a Pt—Mn—X′ alloy, where X′ is selected from the group consisting of Pd, Ir, Rh, Ru, Os, Au, Ag and combinations thereof; a pinned magnetic film contacting said antiferromagnetic layer, wherein a magnetizing direction is pinned by an exchange coupling magnetic field between said pinned magnetic film and said antiferromagnetic layer; wherein said pinned magnetic film includes a first pinned magnetic layer contacting said antiferromagnetic layer and a second pinned magnetic layer and a nonmagnetic intermediate layer therebetween, wherein said first pinned magnetic layer and said second pinned magnetic layer have different thicknesses, and wherein a direction of a synthesized magnetic moment formed by adding a magnetic moment of said first pinned magnetic layer and a magnetic moment of said second pinned magnetic layer points away from said magnetic recording medium; a free magnetic layer; and a nonmagnetic electrically conductive layer formed between said free magnetic layer and said pinned magnetic film, wherein a magnetizing direction of said free magnetic layer is aligned so as to intersect with said magnetizing direction of said pinned magnetic film.
 2. A spin-valve magnetoresistive thin film element according to claim 1, wherein said nonmagnetic intermediate layer comprises a material selected from the group consisting of Ru, Rh, Ir, Cr, Re, Cu, and an alloy thereof.
 3. A spin-valve magnetoresistive thin film element according to claim 2, wherein said material comprises Ru.
 4. A spin-valve magnetoresistive thin film element according to claim 1, wherein at least one pinned layer of said first and said second pinned magnetic layer comprises a material selected from the group consisting of Co, NiFe, CoNiFe, and CoFe.
 5. A spin-valve magnetoresistive thin film element according to claim 4, wherein said material comprises CoFe.
 6. A spin-valve magnetoresistive thin film element according to claim 1, wherein said free magnetic layer comprises two layers of material in intimate contact.
 7. A spin-valve magnetoresistive thin film element according to claim 6, wherein one of the two layers of material comprises a NiFe alloy.
 8. A spin-valve magnetoresistive thin film element according to claim 1, wherein said magnetoresistive thin film element is positioned between an upper shield layer and a lower shield layer, and wherein an upper gap layer resides between said magnetoresistive thin film element and said upper shield layer and a lower gap layer resides between said magnetoresistive thin film element and said lower shield layer.
 9. A spin-valve magnetoresistive thin film element according to claim 1, wherein a ratio of a thickness of said first pinned magnetic layer and a thickness of said second pinned magnetic layer is in a range selected from the group consisting of about 0.53 to about 0.95 and about 1.05 to about 1.8.
 10. A spin-valve magnetoresistive thin film element according to claim 1, wherein a thickness of said first pinned magnetic layer and a thickness of said second pinned magnetic layer are both in a range of about 10 to about 50 angstroms, and wherein an absolute value of thickness of said first pinned magnetic layer minus said film thickness of said second pinned magnetic layer is at least about 2 angstroms.
 11. A spin-valve magnetoresistive thin film element according to claim 1, wherein a thickness of said nonmagnetic intermediate layer is in a range of about 4.0 to about 9.4 angstroms.
 12. A spin-valve magnetoresistive thin film element according to claim 1, wherein a thickness of said nonmagnetic intermediate layer is in a range selected from the group consisting of about 2.8 to about 6.2 angstroms and about 6.8 to about 10.2 angstroms.
 13. A spin-valve magnetoresistive thin film element according to claim 1, wherein a thickness of said antiferromagnetic layer is in a range of about 100 to about 200 angstroms.
 14. A spin-valve magnetoresistive thin film element configured to read a magnetic recording medium, said thin film element comprising: an antiferromagnetic layer, wherein said antiferromagnetic layer comprises one of an X—Mn alloy, where X is selected from the group consisting of Pt, Pd, Ir, Rh, Ru, Os and combinations thereof, and a Pt—Mn—X′ alloy, where X′ is selected from the group consisting of Pd, Ir, Rh, Ru, Os, Au, Ag and combinations thereof; a pinned magnetic film contacting said antiferromagnetic layer, wherein a magnetizing direction is pinned by an exchange coupling magnetic field between said pinned magnetic film and said antiferromagnetic layer, wherein said pinned magnetic film includes a first pinned magnetic layer contacting said antiferromagnetic layer and a second pinned magnetic layer and a nonmagnetic intermediate layer therebetween, wherein a product of saturation magnetization Ms and film thickness t is a magnetic film thickness, wherein said first pinned magnetic film and said second pinned magnetic layer have different magnetic film thicknesses, and wherein a direction of a synthesized magnetic moment formed by adding a magnetic moment of said first pinned magnetic layer and a magnetic moment of said second pinned magnetic layer points away from said magnetic recording medium; a free magnetic layer; and a nonmagnetic electrically conductive layer formed between said free magnetic layer and said pinned magnetic film, wherein a magnetizing direction of said free magnetic layer is aligned so as to intersect with the magnetizing direction of said pinned magnetic film. 